2021 A BVAR TOOLKIT TO ASSESS MACROFINANCIAL RISKS IN BRAZIL AND MEXICO - DOCUMENTOS OCASIONALES N.º 2114

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A BVAR toolkit to assess
macrofinancial risks in Brazil                2021
and Mexico

Documentos Ocasionales
N.º 2114

Erik Andres-Escayola, Juan Carlos Berganza,
Rodolfo Campos and Luis Molina
A BVAR toolkit to assess macrofinancial risks in Brazil and Mexico
A BVAR toolkit to assess macrofinancial risks
in Brazil and Mexico (*)

Erik Andres-Escayola, Juan Carlos Berganza, Rodolfo Campos
and Luis Molina
BANCO DE ESPAÑA

(*) We thank Pedro del Río, Javier Pérez, and Jacopo Timini for their valuable comments and suggestions. The
views expressed in this paper are those of the authors and do not represent the view of the Banco de España or
the Eurosystem. Corresponding authors: erik.andres@bde.es; jcberganza@bde.es; rodolfo.campos@bde.es;
lmolina@bde.es.

Documentos Ocasionales. N.º 2114
June 2021
The Occasional Paper Series seeks to disseminate work conducted at the Banco de España, in the
performance of its functions, that may be of general interest.

The opinions and analyses in the Occasional Paper Series are the responsibility of the authors and, therefore,
do not necessarily coincide with those of the Banco de España or the Eurosystem.

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Reproduction for educational and non-commercial purposes is permitted provided that the source is
acknowledged.

© BANCO DE ESPAÑA, Madrid, 2021

ISSN: 1696-2230 (on-line edition)
Abstract

This paper describes the set of Bayesian vector autoregression (BVAR) models that are
being used at Banco de España to project GDP growth rates and to simulate macrofinancial
risk scenarios for Brazil and Mexico. The toolkit consists of large benchmark models to
produce baseline projections and various smaller satellite models to conduct risk scenarios.
We showcase the use of this modelling framework with tailored empirical applications.
Given the material importance of Brazil and Mexico to the Spanish economy and banking
system, this toolkit contributes to the monitoring of Spain’s international risk exposure.

Keywords: macroeconomic projections, risk scenarios, Bayesian vector autoregressions.

JEL classification: C32, C53, F44, F47.
Resumen

Este documento describe el conjunto de modelos vectoriales autorregresivos bayesianos
(BVAR) que se utilizan en el Banco de España para elaborar proyecciones de crecimiento del
PIB y simular escenarios de riesgo macrofinanciero para Brasil y México. Esta herramienta
está compuesta por un modelo base para elaborar proyecciones de referencia y varios
modelos satélite para llevar a cabo escenarios de riesgo. Ilustramos el uso de este marco
de modelización con aplicaciones empíricas específicas. Dada la importancia material de
Brasil y México para la economía española y su sistema bancario, este conjunto de modelos
contribuye al seguimiento de la exposición internacional de España.

Palabras clave: proyecciones macroeconómicas, escenarios de riesgo, vectores
autorregresivos bayesianos.

Códigos JEL: C32, C53, F44, F47.
Contents

Abstract     5

Resumen       6

1   Introduction        8

2   Methodology          10

    2.1    Framework          10
    2.2    General models           11
    2.3    Conditional forecasts          13
    2.4    Satellite models         14
    2.5    Auxiliary models         16
    2.6    Data    18

3   Empirical Results          20

    3.1    Validations      20
    3.2    Applications       22

4   Concluding Remarks              26

References        27

Appendix A:       Forecasting Exercice         30

Appendix B:       Historical Decompositions and Potential Output   35

Appendix C:       Technical Assumptions         39

Appendix D:       Data Details           40
1 Introduction

The analysis of the Latin American economies has a long tradition at the Banco de España, as

1    Introduction
evidenced by the continued publication of a half-yearly report on the region since September

2003. Over time, the analysis has become more sophisticated which has led to the use
The analysis of the Latin American economies has a long tradition at the Banco de España, as
of macroeconometric
the   Eurosystem4 and tools              tailored obtained
                                 the forecasts        for each country.
                                                                   from theirAmonguse were  thealso
                                                                                                  newnottools   in use, vector
                                                                                                            compatible         with
evidenced by the continued publication of a half-yearly report on the region since September
autoregression
assumptions            (VAR) models
                    underlying                have proved
                                    the forecasts       for the to Spanish
                                                                    be a suitable
                                                                               economy andthatflexible
                                                                                                   are kit   to study
                                                                                                         regularly          the co-
                                                                                                                       published
2003. Over time, the analysis has become more sophisticated                                     which    has  led     to  the   use
movement        of   macroeconomic            variables    in  these    economies.
by Banco de España. The current methodology solves this problem. Moreover, from a
                                                                                       1
                                                                                           Starting    with   the     half-yearly
of macroeconometric tools tailored for each country. Among the new tools in use, vector
report     of 2020 (Banco
methodological          point ofdeview,
                                      España      (2020)),BVAR
                                             the current       VAR models
                                                                       modelshave        been and
                                                                                  for Brazil     usedMexico
                                                                                                        to guide     and inform
                                                                                                                  follow    closely
autoregression (VAR) models have proved to be a suitable and flexible kit to study the co-
forecasts
the           for the two
      methodology               largest
                           of the  suiteeconomies
                                             of BVAR modelsof the region:
                                                                     for the Brazil
                                                                                Spanish  and    Mexico.which
                                                                                            economy,       In thisis paper,
                                                                                                                       describedwe
movement of macroeconomic variables in these economies. Starting with the half-yearly  1

in detail the
describe           suite of Bayesian
             by Leiva-Leon         (2017).VAR (BVAR) models that are currently in use to inform those
report of 2020        (Banco de España (2020)), VAR models have been used to guide and inform
projections.     2
                    These
     The toolkit for Brazil   two countries
                                     and Mexico   are the    only countries—other
                                                       contains     a relatively large than set ofSpain—for
                                                                                                    variables (10  which    Banco
                                                                                                                       variables)
forecasts for the two largest economies of the region: Brazil and Mexico. In this paper, we
de España
and     includespublishes      regularassumptions
                     all technical         forecasts. The       advantage
                                                            in the             of theseB/MPE
                                                                     Eurosystem’s          models overthat global      structural
                                                                                                             are relevant       for
describe the suite of Bayesian VAR (BVAR) models that                              are currently in use to inform those
modelsand
Brazil      such    as NiGEM
                Mexico.      A largeorbenchmark
                                           Global Economic
                                                         model that  Model    3
                                                                         includesis all
                                                                                     that    they are
                                                                                         variables        better
                                                                                                      is used        adapted toa
                                                                                                               to determine
projections. These two countries are the only countries—other than Spain—for which Banco
                 2
the characteristics
baseline     projection for  of the
                                 GDP  economies        of the region
                                          growth, whereas        smaller  and   allow versions
                                                                            reduced      for an introduction
                                                                                                    of it are usedoftorelevant
                                                                                                                           predict
de España publishes regular forecasts. The advantage of these models over global structural
idiosyncratic
the   impact ofvariables.
                      changes ofFurther,
                                      technical  thisassumptions
                                                       flexibility and      empirical
                                                                       or the             nature on
                                                                                 steady-state       of BVARs
                                                                                                        the growth makes      them
                                                                                                                         forecast.
models such as NiGEM or Global Economic Model is that they are better adapted to
                                                                              3
better suited
Following           for designing
               Leiva-Leon        (2017),adequate
                                             we define anda reasonable
                                                              number of risk       scenarios.
                                                                              satellite   models for Brazil and Mexico
the characteristics of the economies of the region and allow for an introduction of relevant
thatThere      have
         capture    thebeen     prior in-house
                           mechanisms         of theefforts     of using
                                                       particular     risk macroeconometric
                                                                             scenario to be simulated. tools to Thestudy     Latin
                                                                                                                         satellite
idiosyncratic variables. Further, this flexibility and empirical nature of BVARs makes them
American
models foreconomies.             For example,
                 scenarios concerning                 Estrada et
                                                  deviations      in al.
                                                                      the(2020)     describe
                                                                             technical           BVAR models
                                                                                           assumptions                 that were
                                                                                                             are structurally
better suited for designing adequate and reasonable risk scenarios.
estimated via
identified     for sign
                     Brazil,    Mexico, Turkey,
                            restrictions,               Chile, by
                                               as described      andUhlig
                                                                        Peru.(2005).
                                                                                 However, Forthese     prior models
                                                                                                the scenario              did not
                                                                                                                  that changes
     There have been prior in-house efforts of using macroeconometric tools to study Latin
closely
the        tie the forecasts
       steady-state       of GDPtogrowth,the technical
                                                   we useassumptions
                                                               an auxiliarythat  modelare toused   for producing
                                                                                                estimate    potentialforecasts
                                                                                                                           output
American economies. For example, Estrada et al. (2020) describe BVAR models that were
within
using athe      Eurosystem.
            production               Therefore,
                              function.       In this their   results
                                                         paper,     we were     difficult
                                                                         simulate           to square
                                                                                      scenarios           with
                                                                                                    related   tothe     forecasts
                                                                                                                    fluctuations
estimated for Brazil, Mexico, Turkey, Chile, and Peru. However, these prior models did not
for foreign
in    Brazil demand,
                and Mexico         in thein (Broad)
                               changes                      Macroeconomic
                                                the commodity                      Projections
                                                                       prices, shifts                Exercise
                                                                                           in domestic            (B/MPE)
                                                                                                            economic             of
                                                                                                                             policy
closely
     1     tie the forecasts        to the technical assumptions that are used for producing forecasts
the    See for example
      Eurosystem            the the
                           and    half-yearly
                                       forecastsreport   Banco de
                                                     obtained         España
                                                                   from    their(2016)   or thealso
                                                                                  useoutput
                                                                                         were     half-yearly
                                                                                                       notcouldreport Banco
                                                                                                            compatible           de
                                                                                                                   witness with
                        4
uncertainty
España (2017).
                  and    financial   tensions,     and    long-term      effects  on              as we                        with
within
     2     the Eurosystem. Therefore, their results were difficult to square with the forecasts
       We consider
assumptions             these two the
                   underlying       Latinforecasts
                                             Americanfor  economies    as they
                                                             the Spanish         are of major
                                                                               economy      that importance
                                                                                                   are regularly for the    Spanish
                                                                                                                       published
the   COVID-19         pandemic.
economy and they represent the largest exposure of the Spanish banking system among emerging economies,
for Brazil and Mexico in the (Broad) Macroeconomic Projections Exercise (B/MPE) of
see Box
by   Banco 2 in de
                Banco     de España    (2020).
     The rest
     3             ofEspaña.
                        the paper  The      current methodology
                                       is structured       as follows: solves       this 2problem.
                                                                           in section        we explainMoreover,
     1 These are two popular models used in central banks from the National Institute of Economic and Social
                                                                                                            the methodolog-from a
      See for example the half-yearly report Banco de España (2016) or the half-yearly report Banco de
Research   and Oxford
methodological        Economics.
                   point of view,
España
ical2
         (2017).
      framework,    the details of the
                                    thecurrent BVAR
                                        theoretical   models
                                                    BVAR     for Brazil
                                                         models   used and  Mexico
                                                                        to carry outfollow closely
                                                                                     the baseline
      We consider these two Latin American economies as they are of major importance for the Spanish
the methodology
economy and they
projections       of risk
                 the the suite
            and represent the    of BVAR
                              largest
                          scenarios,        models
                                      exposure
                                       and the    the for
                                               ofdata     thefor
                                                      Spanish
                                                       used    Spanish
                                                              banking   economy,
                                                                      system     which
                                                                             among
                                                                 the empirical           is
                                                                                         Indescribed
                                                                                   emerging
                                                                               exercise.    economies,
                                                                                            section 3
see Box 2 in Banco de España (2020).
in
wedetail
   3
     Theseby
   present areLeiva-Leon
             the           (2017).
               twoestimation
                   popular models usedand
                             results   in central banks
                                            discuss     from the National Institute of Economic and Social
Research and Oxford Economics.                      1our findings, and in section 4 we conclude.
   The
   4     toolkitonfor
     For details    theBrazil and Mexico
                        Eurosystem’s       contains
                                     projection       a relatively
                                                exercises            large
                                                          please refer      setwebsite
                                                                       to the   of variables
                                                                                       here. (10 variables)

and includes all technical assumptions in the Eurosystem’s B/MPE that are relevant for
                   8
                                           1 includes all variables is used to determine a
Brazil and Mexico. A large benchmark model that
 BANCO DE ESPAÑA       DOCUMENTO OCASIONAL N.º 2114

baseline projection for GDP growth, whereas smaller reduced versions of it are used to predict
the Eurosystem4 and the forecasts obtained from their use were also not compatible with
assumptions underlying the forecasts for the Spanish economy that are regularly published

by Banco de España. The current methodology solves this problem. Moreover, from a
methodological point of view, the current BVAR models for Brazil and Mexico follow closely
the methodology of the suite of BVAR models for the Spanish economy, which is described

in detail by Leiva-Leon (2017).
    The toolkit for Brazil and Mexico contains a relatively large set of variables (10 variables)
and includes all technical assumptions in the Eurosystem’s B/MPE that are relevant for
Brazil and Mexico. A large benchmark model that includes all variables is used to determine a

baseline projection for GDP growth, whereas smaller reduced versions of it are used to predict
the impact of changes of technical assumptions or the steady-state on the growth forecast.
Following Leiva-Leon (2017), we define a number of satellite models for Brazil and Mexico

that capture the mechanisms of the particular risk scenario to be simulated. The satellite
models for scenarios concerning deviations in the technical assumptions are structurally
identified via sign restrictions, as described by Uhlig (2005). For the scenario that changes

the steady-state of GDP growth, we use an auxiliary model to estimate potential output

using a production function. In this paper, we simulate scenarios related to fluctuations
in foreign demand, changes in the commodity prices, shifts in domestic economic policy

uncertainty and financial tensions, and long-term effects on output as we could witness with

the COVID-19 pandemic.
    The rest of the paper is structured as follows: in section 2 we explain the methodolog-
ical framework, the details of the theoretical BVAR models used to carry out the baseline

projections and the risk scenarios, and the data used for the empirical exercise. In section 3
we present the estimation results and discuss our findings, and in section 4 we conclude.
    4
        For details on the Eurosystem’s projection exercises please refer to the website here.

                                                         2

 BANCO DE ESPAÑA   9   DOCUMENTO OCASIONAL N.º 2114
2 Methodology

In this section, we define the framework and models of the toolkit used for producing baseline
2    Methodology
projections and risk scenarios.                   We also refer to the data included in the models for the

empirical results.
In this section, we define the framework and models of the toolkit used for producing baseline
projections and risk scenarios. We also refer to the data included in the models for the
2.1       Framework
empirical results.
Our modelling strategy to conduct growth projections and simulate risk scenarios entails
two
2.1 steps. The first step consists of defining a benchmark model capturing most of the
      Framework
fundamental macrofinancial relations of the economies of Brazil and Mexico. We then run
Our modelling strategy to conduct growth projections and simulate risk scenarios entails
conditional forecasts where the conditions are anchored to the technical assumptions of the
two steps. The first step consists of defining a benchmark model capturing most of the
Eurosystem’s B/MPE.5 This benchmark model is used to carry out the baseline projection of
fundamental macrofinancial relations of the economies of Brazil and Mexico. We then run
GDP growth. Then, four satellite models are defined which are in essence reduced versions
conditional forecasts where the conditions are anchored to the technical assumptions of the
of the benchmark model. Fewer variables enable for better identification and to focus on
Eurosystem’s B/MPE.5 This benchmark model is used to carry out the baseline projection of
the mechanisms for the particular scenario considered. For each of the satellite models,
GDP growth. Then, four satellite models are defined which are in essence reduced versions
we first simulate a central forecast that includes the same technical assumptions or steady-
of the benchmark model. Fewer variables enable for better identification and to focus on
state as the benchmark model. The risk scenario then includes deviations of the technical
the mechanisms for the particular scenario considered. For each of the satellite models,
assumptions for some specific variables or a different steady-state. Finally, we compute the
we first simulate a central forecast that includes the same technical assumptions or steady-
difference between the central and the scenario forecasts in the satellite model to obtain the
state as the benchmark model. The risk scenario then includes deviations of the technical
net effect that we add to the baseline projection. By isolating this effect, and integrating
assumptions for some specific variables or a different steady-state. Finally, we compute the
it into the baseline projection, we measure the impact of each scenario separately and shed
difference between the central and the scenario forecasts in the satellite model to obtain the
light on the sensitivity of our projections.
net effect that we add to the baseline projection. By isolating this effect, and integrating
    The ten model variables are split up into four global and six local ones. For the group
it into the baseline projection, we measure the impact of each scenario separately and shed
of global variables, we construct a measure of foreign demand (EXD) for each country as
light on the sensitivity of our projections.
a weighted average of real imports from the main trade partners. The weights are based
    The ten model variables are split up into four global and six local ones. For the group
on bilateral exports. Further, we include oil prices to proxy commodity prices (OIL), a
of global variables, we construct a measure of foreign demand (EXD) for each country as
    5
measure    for global
      For more         financial
               details on how we turbulences     (VIX)
                                   adopt the B/MPE       and the
                                                      technical    US short-term
                                                                assumption         interest exercises
                                                                           to our projection rate to proxy
                                                                                                      at the
a weighted
Banco         average
        de España,       of real
                   see Box        imports
                            3 in the        from
                                     report on the the
                                                   Latinmain  tradeeconomy,
                                                         American    partners.   The
                                                                             Banco     weights(2020).
                                                                                    de España    are based
foreign monetary policy (FFU). We assume that global variables affect local variables, but
on bilateral exports. Further, we include oil prices to proxy commodity prices (OIL), a
not 5 the other way around (i.e., we assume block      3     exogeneity). In this way, we can better
    For more details on how we adopt the B/MPE technical assumption to our projection exercises at the
Banco de the
capture  España, see Box 3 inspillover
             international    the reporteffects
                                         on the Latin
                                                that American  economy,
                                                      potentially affectBanco de España
                                                                         the growth     (2020).
                                                                                     projections    of
Brazil and Mexico. The local variables are real GDP growth (GDP), CPI core inflation
           10
 BANCO DE ESPAÑA                             3
                   DOCUMENTO OCASIONAL N.º 2114

(INF), bilateral exchange rate vis-à-vis the USD (FXR), the EMBI+ as a measure of the
sovereign spread that proxies external financing costs (EMB), a measure of economic policy
measure
measure for
        for global
            global financial
                   financial turbulences
                             turbulences (VIX)
                                         (VIX) and
                                               and the
                                                   the US
                                                       US short-term
                                                          short-term interest
                                                                     interest rate
                                                                              rate to
                                                                                   to proxy
                                                                                      proxy
foreign
foreign monetary
        monetary policy
                 policy (FFU).
                        (FFU). We
                               We assume
                                  assume that
                                         that global
                                              global variables
                                                     variables affect
                                                               affect local
                                                                      local variables,
                                                                            variables, but
                                                                                       but
not
not the
    the other
        other way
              way around
                  around (i.e.,
                         (i.e., we
                                we assume
                                   assume block
                                          block exogeneity).
                                                exogeneity). In
                                                             In this
                                                                this way,
                                                                     way, we
                                                                          we can
                                                                             can better
                                                                                 better
capture
capture the
        the international
            international spillover
                          spillover effects
                                    effects that
                                            that potentially
                                                 potentially affect
                                                             affect the
                                                                    the growth
                                                                        growth projections
                                                                               projections of
                                                                                           of
Brazil
Brazil and
       and Mexico.
           Mexico. The
                   The local
                       local variables
                             variables are
                                       are real
                                           real GDP
                                                GDP growth
                                                    growth (GDP),
                                                           (GDP), CPI
                                                                  CPI core
                                                                      core inflation
                                                                           inflation
(INF),
(INF), bilateral
       bilateral exchange
                 exchange rate
                          rate vis-à-vis
                               vis-à-vis the
                                         the USD
                                             USD (FXR),
                                                 (FXR), the
                                                        the EMBI+
                                                            EMBI+ as
                                                                  as aa measure
                                                                        measure of
                                                                                of the
                                                                                   the
sovereign
sovereign spread
          spread that
                 that proxies
                      proxies external
                              external financing
                                       financing costs
                                                 costs (EMB),
                                                       (EMB), aa measure
                                                                 measure of
                                                                         of economic
                                                                            economic policy
                                                                                     policy
uncertainty
uncertainty (EPU),
            (EPU), and
                   and the
                       the policy
                           policy interest
                                  interest rate
                                           rate (INT)
                                                (INT) for
                                                      for the
                                                          the two
                                                              two Latin
                                                                  Latin American
                                                                        American countries.
                                                                                 countries.
     In
     In Figure
        Figure 11 we
                  we illustrate
                     illustrate our
                                our approach
                                    approach to
                                             to producing
                                                producing the
                                                          the baseline
                                                              baseline projections
                                                                       projections and
                                                                                   and the
                                                                                       the risk
                                                                                           risk
scenarios.
scenarios.

Figure
Figure 1:
        1: Summary
           Summary of of the
                         the modelling
                             modelling framework
                                       framework to
                                                  to produce
                                                     produce the
                                                             the GDP
                                                                 GDP growth
                                                                     growth baseline
                                                                            baseline pro-
                                                                                     pro-
jections and the risk scenarios of Brazil and Mexico
jections and the risk scenarios of Brazil and Mexico

Notes: The
Notes:  The benchmark
              benchmark model
                           model is
                                  is used
                                     used for
                                          for the
                                              the baseline
                                                  baseline projection
                                                           projection which
                                                                        which is
                                                                               is conditioned
                                                                                  conditioned on
                                                                                               on technical
                                                                                                   technical assump-
                                                                                                             assump-
tions.
tions. The different satellite models are used to produce a central and a scenario forecast that makes
       The  different  satellite models are used to produce   a central and  a scenario  forecast that makes up
                                                                                                              up the
                                                                                                                 the
net
net effect of the risk scenario at hand. This net effect is added to the baseline projection to measure the
    effect of  the risk  scenario at hand.  This  net effect is added   to the  baseline  projection to measure  the
impact
impact of
        of the
           the risk
                risk scenario.
                     scenario.

                                                         44
2.2       General Models

For the projection exercises we estimate large VARs using Bayesian inference. These models
have become an essential empirical tool for central banks to conduct macroeconomic analysis.

As explained in detail in Bańbura et al. (2010) and Giannone et al. (2015) larger systems
and Bayesian estimation are extremely appealing for forecasting applications. Based on
 BANCO DE ESPAÑA   11   DOCUMENTO OCASIONAL N.º 2114

marginal likelihoods and in-sample criteria, we specify models with four lags and Minnesota-
type priors. These priors are the most common ones used in the literature and they assume
have become an essential empirical tool for central banks to conduct macroeconomic analysis.

As explained in detail in Bańbura et al. (2010) and Giannone et al. (2015) larger systems
and Bayesian estimation are extremely appealing for forecasting applications. Based on
marginal likelihoods and in-sample criteria, we specify models with four lags and Minnesota-

type priors. These priors are the most common ones used in the literature and they assume

2.2 the
that  General  Models
        VAR coefficients behave according to a normal distribution.6 Then, it is left to
the researcher to specify the values for the mean and covariance of the distribution, known
For the projection exercises we estimate large VARs using Bayesian inference. These models
as the hyperparameters. For the Minnesota-type prior the hyperparameter values follow a
have become an essential empirical tool for central banks to conduct macroeconomic analysis.
certain rationale.7
As explained in detail in Bańbura et al. (2010) and Giannone et al. (2015) larger systems
     Finally, Bayes’ formula is applied to combine information of the prior distribution and
and Bayesian estimation are extremely appealing for forecasting applications. Based on
the likelihood function, resulting in a posterior distribution. From this latter distribution
marginal likelihoods and in-sample criteria, we specify models with four lags and Minnesota-
one obtains draws to compute the functions and estimates of interest (i.e., impulse response
type priors. These priors are the most common ones used in the literature and they assume
functions (IRFs) and forecasts).8 In practical terms, the estimation is implemented using
that the VAR coefficients behave according to a normal distribution.6 Then, it is left to
Markov chain Monte Carlo (MCMC) algorithms (i.e., Gibbs sampling).9
the researcher to specify the values for the mean and covariance of the distribution, known
     The multivariate time-series model for periods t = 1, . . . , T consists of a n × 1 vector of
as the hyperparameters. For the Minnesota-type prior the hyperparameter values follow a
variables {yt }Tt=1 , n × n matrices of coefficients Ai , i = 1, . . . , p capturing the dynamics of the
certain
pth       rationale.
     lagged
                       7
              system, a n × 1 vector of constants C and a n × 1 vector of error terms εt with
    6
      In contrast
pth lagged         to theafrequentist
              system,       n × 1 vector approach,    Bayesian C
                                               of constants     inference
                                                                   and a treats
                                                                           n × 1 the  data of
                                                                                   vector   as error
                                                                                                deterministic
                                                                                                      terms εand    the
                                                                                                               t with
     Finally,
parameter      Bayes’
            space  as    formula
                      stochastic.   is
                                  This  applied
                                         type  of   to  combine
                                                  inference has    information
                                                                become             of
                                                                         increasingly the  prior
                                                                                      popular
zero-mean and positive-definite n × n covariance matrix Σ. This data generating process is     as adistribution
                                                                                                    shrinkage     and
                                                                                                               method
to resolve overparametrization
zero-mean                         issues, noften
              and positive-definite          × nencountered
                                                    covarianceinmatrix
                                                                    empirical
                                                                           Σ.macroeconomics.      Given that
                                                                               This data generating           the time
                                                                                                          process    is
the  likelihood
series in Brazil   function,
                  and   Mexico  resulting
                                are           in
                                     relatively   a  posterior
                                                  short
assumed to evolve according to the following VAR(p):     compareddistribution.
                                                                    to advanced   From    this
                                                                                  economies,    latter
                                                                                              the  use  distribution
                                                                                                       of a shrinkage
method is particularly
assumed                   appropriateto
            to evolve according         in the
                                            our application.
                                                 following VAR(p):
one7obtains
      Littermandraws
                 (1986)to   compute
                         describes  the the    functions
                                          specific         and
                                                   structure     estimates of interest
                                                             of hyperparameters            (i.e., impulse
                                                                                   in the Minnesota   prior.response
                                                                                                             They are
applied to the whole block of coefficients and are therefore a global shrinkage method to reduce overfitting.
functions
For           (IRFs)
     the Minnesota         and
                  yt =prior,      forecasts).
                               + the
                                                  8
                                                     In practical
                                      residual covariance        matrix terms,
                                                                          is estimatedthe from
                                                                                             estimation
                                                                                                    the εmodel
                                                                                                 with           is via
                                                                                                                    implemented
                                                                                                                       OLS, whereasusing   other
                                                                                                                                             (1)
                           C      A 1 yt−1 + A2 yt−2 + · · · + Ap yt−p + εt ,                             t ∼ N (0, Σ).
approaches treat  yt is= asC unknown,
                               + A1 yt−1and +A   assume
                                                    y
                                                   2 t−2
                                                            an
                                                            +  ·inverse
                                                                 · · +  A Wishart
                                                                             y
                                                                           p t−p    + distribution
                                                                                        εt ,     with   as
                                                                                                         εt
                                                                                                            the
                                                                                                             ∼   prior.
                                                                                                                 N   (0,   We
                                                                                                                           Σ).  choose   the  hy-
                                                                                                                                             (1)
Markov     chainbyMonte
perparameters           runningCarlo
                                   a grid (MCMC)
                                           search algorithmalgorithms        (i.e., Gibbs
                                                                   that automatically             sampling).
                                                                                              selects  suitable9hyperparameters based
on the
     Themarginal      likelihood. model
           open-economy              Then, we     partly adjust
                                               contains              the hyperparameter
                                                              variables       for the global       values
                                                                                                      blockbased(G)onand this for
                                                                                                                               information.
                                                                                                                                     the local
    8
     The   multivariate
      Usually,    the mediantime-series
           open-economy            ofmodel        model
                                               contains
                                       the posterior      is for   periods
                                                              variables
                                                              reported    and fortused
                                                                                   =the1,asglobal
                                                                                          . . the    consists
                                                                                                      block
                                                                                              . , T point       (G)of and
                                                                                                            estimate.  a nNote×      vector
                                                                                                                               for1 that
                                                                                                                                     the  local
                                                                                                                                          underof
Bayesian   inference
block (L) consisting     the   model   uncertainty     is  much    better   captured     since    one  computes
                               of variables for Brazil (BR) and Mexico (MX). Hence, yt = {ytG , ytL }, with           an   entire
                                                                                                                                G distribution
                                                                                                                                      L
variables
block
for the (L)      t }t=1 , n ×
             consisting
         parameters.
             {y      T
                                    matricesfor
                               ofnvariables       of Brazil
                                                      coefficients
                                                                 (BR) A  and
                                                                           i , i Mexico       , p capturing
                                                                                  = 1, . . .(MX).       Hence,the   yt =dynamics
                                                                                                                             {yt , yt },ofwith
                                                                                                                                            the
    9
      For the  computational        implementation        of the   models   we    used  the
L =6 (BR, M X). Each superscript indicates a group of variables (10 variables in total, 4 in developer     version    of  the BEAR      toolbox.
   = In
Refer
L      tocontrast
          Dieppe
       (BR,   M X).    to al.
                      et   the
                           Each frequentist
                              (2016)superscriptapproach,
                                       for further            Bayesian
                                                      indicates
                                                     details.              inference
                                                                      a group            treats the (10
                                                                                    of variables        datavariables
                                                                                                                as deterministic
                                                                                                                              in total, and4the
                                                                                                                                              in
parameter space as stochastic. This type of inference has become increasingly                           popular as a shrinkage method
the G group and 6 in the L group). In particular we have ytG = (EXDt , OILt , V IXt , F F Ut )⊤
                                                                                            G
to resolve
the  G groupoverparametrization
                   and 6 in the L issues,group).  often
                                                      In encountered
                                                           particular we    in empirical
                                                                                  have yt macroeconomics.
                                                                                               = (EXDt , OILGiven               that the time
                                                                                                                        t , V IXt , F F Ut )
                                                                                                                                               ⊤
series in
        L Brazil and Mexico are relatively short compared to ⊤advanced economies, the use of a shrinkage
and ytL = (GDPt , IN Ft , F XRt , EM Bt , EP Ut , IN Tt )⊤ in the case of the benchmark model
method
and   y is=particularly
              (GDPt , IN       appropriate
                                 Ft , F XRin      our application.
                                              t , EM Bt , EP Ut5, IN Tt ) in the case of the benchmark model
    7 t
      Litterman (1986) describes the specific structure of hyperparameters in the Minnesota prior. They are
and subsets from both blocks in the case of the satellite models. The block exogeneity
applied
and      to the whole
       subsets      from blockbothofblocks
                                        coefficients
                                                 in theand case
                                                              are therefore
                                                                     of the asatellite
                                                                                   global shrinkage
                                                                                                models.method  The toblock reduceexogeneity
                                                                                                                                     overfitting.
For the Minnesota prior, the residual covariance matrix is estimated from the model via OLS, whereas other
assumption entails imposing zero-restrictions on the coefficient matrices so to cancel out
approaches treat
assumption             is as unknown,
                   entails     imposingandzero-restrictions
                                                 assume an inverse on     Wishart     distribution as
                                                                                the coefficient             the prior.soWe
                                                                                                        matrices             tochoose
                                                                                                                                  cancel theout
                                                                                                                                              hy-
perparameters   10by running       aGgrid search algorithm that automatically selects suitable hyperparameters based
past effects10 of ytL on ytG :
                           L
on theeffects
past    marginal of   likelihood.
                         yt on ytThen, :     we partly adjust the hyperparameter values based on this information.
    8
      Usually, the median of the posterior is reported and used as the point estimate. Note that under
                                                                                             
Bayesian inference themodel          uncertainty
                                                     is much    better captured     since   one computes
                                                                                                          G  an entire distribution
                                                            p
for the parameters. ytG 
                                  G
                                              c
                                             ∑          ∑ p 
                                                                   a           0     t−i y G
                                                                                                         εG
                                                1                    11,i                    G               t 
    9
      For the computational  yt 
                                       = c1 
                                    implementation
                                                  + of the      a11,i we0used
                                                                models            
                                                                                      theyt−i   +
                                                                                             developer
                                                                                                           εt  . of the BEAR toolbox.
                                                                                                         version                            (2)
Refer to Dieppe et al. (2016)    L =   +
                                ytL for further
                                              c2 details. i=1     a21,i a22,i             L  +  L .
                                                                                           yt−i             εLt                              (2)
                                                                                             L
                                  yt                 c2    i=1     a21,i a22,i            yt−i             εt

     One might 12
  BANCO DE ESPAÑA   be interested in having an economic interpretation of the shocks, and for
                      DOCUMENTO OCASIONAL N.º 2114

     One might be interested in having an economic5       interpretation of the shocks, and for
this, one needs to define the contemporaneous relationships between variables. Let Dj , j =
this, one needs to define the contemporaneous relationships between variables. Let Dj , j =
0, . . . , p capture such structural relationships, K be the constants and ηt be the structural
The open-economy model contains variables for the global block (G) and for the local
block (L) consisting of variables for Brazil (BR) and Mexico (MX). Hence, yt = {ytG , ytL }, with
L = (BR, M X). Each superscript indicates a group of variables (10 variables in total, 4 in
the G group and 6 in the L group). In particular we have ytG = (EXDt , OILt , V IXt , F F Ut )⊤
pth lagged system, a n × 1 vector of constants C and a n × 1 vector of error terms εt with
and ytL = (GDPt , IN Ft , F XRt , EM Bt , EP Ut , IN Tt )⊤ in the case of the benchmark model
zero-mean and positive-definite n × n covariance matrix Σ. This data generating process is
and subsets from both blocks in the case of the satellite models. The block exogeneity
assumed to evolve according to the following VAR(p):
established by
assumption  entails DDi , C =zero-restrictions
               Ai =imposing      DK, εt = Dηt on  andthe    DΓD⊤ , with
                                                      Σ =coefficient matrices  D0−1to. To
                                                                          D = so          recover
                                                                                       cancel out
the structural
past effects10 ofmodel    ytG : its reduced-form or disentangle ηt from εt , one needs to adopt an
                  ytL onfrom
             yt = C + A1 yt−1 + A2 yt−2 + · · · + Ap yt−p + εt , with εt ∼ N (0, Σ).                  (1)
identification strategy   to
                          restrict   the contemporaneous
                                                                matrix D.
                                                                           
                                              p
   The open-economy
                         G
                     yt  model  ccontains
                                       1    ∑variables
                                                 a11,i for 0        G
                                                                theglobal
                                                                    yt−i  blockG
                                                                             εt (G)
                                                                                    and for the local
                      = +                                          +  .                     (2)
2.3     Conditional    y L
                            Forecasts
block (L) consisting oftvariables 2for Brazil (BR)
                                     c       i=1   a21,iand22,i
                                                          a         y L
                                                             Mexico t−i        ε L
                                                                      (MX). Hence,
                                                                                 t  yt = {yt , yt }, with
                                                                                           G    L

L  = (BR,
Note           MtheX).
         thatmight        Each projection
                      baseline    superscriptand indicates   a group    of variables  (10out
                                                                                           variables     inconditional
                                                                                                             total, 4 in
     One               be interested     in havingthe   anrisk  scenarios
                                                            economic        are carried
                                                                         interpretation        through
                                                                                          of the     shocks,      and for
the   G
forecasts  group   and  6   in the  L group).    In particular    we  have  y G
                                                                                = (EXD      , OIL    , V IX    , F  F Ut ) ⊤
         one in   termsto of   sequences    of observables, asrelationships
                                                                   describedt bybetween
                                                                                  Waggoner      and ZhaLet  (1999).
                                                                                                                  Dj , j In
                                                                                          t        t         t
this,         needs         define  the contemporaneous                                     variables.                    =
and       L
        yt = (GDP
particular,             t , IN Ft , F XR
                 the conditional          t , EMwhen
                                      forecasts    Bt , EP Ut , IN
                                                         using      Tt ) in the describe
                                                                 this
                                                                        ⊤
                                                                                  case of the benchmark             model
0, . . . , p capture    such structural       relationships,    K   betechnique
                                                                        the constants andthe   ηt most
                                                                                                  be the  likely    future
                                                                                                             structural
and
path subsets        from both blocks
         of the unconditioned        variablein given
                                                the case    of the imposed
                                                        conditions    satellite for
                                                                                models.
                                                                                    the restThe variables
                                                                                                   block exogeneity
innovations       with zero-mean        and structural     covariances     Γ. Therefore,    theofstructural      (i.e.,
                                                                                                                  VAR(p)the
assumption
likely     future  entails imposing zero-restrictions on the coefficient matrices so to cancel out
is given     by: path of GDP growth given the assumed path of the rest of the variables). As
past    effectsin10Antolín-Díaz
explained            of ytL on ytG : et al. (2021), the structural identification of D does not play a role

                      
in how theDconditional            arey constructed
                           forecasts                        +
                                                         using  
                                                                this   withη ∼
                                                                  ηt , approach.   N (0, Γ). structural
             0 yt = K + D    1 yt−1 + D 2 t−2 + · · · + Dp yt−p                 t However,           (3)
                                            p
                       y G
                      t   1     c      ∑     a
                                                11,i     0       y G
                                                               t−i   t   ε G
identification still 
                     helpsto= gain
                                  insights
                                         +     on why weobserve
                                                                      this
                                                                         + forecasting
                                                                                  .                 (2)
                                                                                           path for the
                       ytL          c2     i=1   a21,i a22,i        L
                                                                 yt−i         εLt
    As a result,variable
unconditioned     the linkinbetween    the reduced-form
                               the context  of a “what if”VAR    and the
                                                             scenario.     structural
                                                                        Therefore,  forcounterpart
                                                                                                    11
                                                                                        the benchmark  is
   10
     This restriction
established   bythe     implies
                           DDithat
                                 , C local variables are not  Granger
                                                            and       causing
                                                                       DΓD⊤global
                                                                              , withvariables.
model  wemight
           run       i central  forecasts  based   on  thet technical assumptions   and  obtain0 .the
                                                                                                   Tobaseline
                                                                                                      recover
                                                                                               −1
   11One
                   A
                   be   =interested   =
                                      in DK,
                                          havingεt =
                                                   an Dηeconomic Σ=interpretation    Dthe
                                                                                    of   =  Dshocks,  and for
     The key difference between equation 1 and 3 is that the reduced-form VAR is a mere statistical     model,
for which estimation is possible.  Conversely,
the  structural
projection
this,           model
            without
      one needs         fromthe
                      adopting
                  to define    itsany specificthe
                                   reduced-form   structural
                                               structural
                                  contemporaneous
                                                             augmentation
                                                  or disentangle      frommakes
                                                           identification.
                                                      relationships
                                                                                  theneeds
                                                                           εt , one
                                                                           Contrary,
                                                                   ηt between         modelto
                                                                                            economically
                                                                                           Letadopt
                                                                                       for the
                                                                                variables.      Dj , j an
                                                                                               satellite=
identification
models
   . . . , p used  strategy
                  for
              capture        to restrict
                      simulating         the contemporaneous
                                  risk scenarios,
                       such structural            it makes
                                        relationships,     sensematrix
                                                                to identify
                                                                       D. structural shocks to gain
0,                                                    6 K be the constants and ηt be the structural
additional insights
innovations         regardingand
            with zero-mean    the structural
                                   impact of covariances
                                             the scenariosΓ.on the baseline
                                                             Therefore, the projections.
                                                                            structural VAR(p)
2.3        Conditional Forecasts
is given by:
2.4   Satellite
Note that          Models
          the baseline projection and the risk scenarios are carried out through conditional
forecasts     0 yt = of
          inDterms   K sequences
                        + D1 yt−1 +   2 yt−2 + · · · +
                                  ofDobservables,    asD p yt−p + ηtby
                                                        described      with ηt ∼ and
                                                                    , Waggoner           Γ). (1999). (3)
                                                                                   N (0,Zha           In
In the spirit   of Leiva-Leon  (2017)  we partially    set-identify  the satellite models using    sign
particular, the
restrictions. 12 conditional forecasts when using this technique describe the most likely future
                 For conducting the sign restriction identification, one needs to focus on εt =
    As a result, the link between the reduced-form VAR and the structural counterpart11 is
path
Dηt toofrestrict
         the unconditioned  variable given
                 the contemporaneous       conditions
                                        impact matrix imposed   forcase
                                                       D. For the   the rest of variables (i.e.,
                                                                        of sign-identified       the
                                                                                            models
   10
        This restriction implies that local variables are not Granger causing global variables.
likely
we 11
       future
      The
    have  key
          D=   path
                P Q, of
              difference  GDPP growth
                         between
                       where     equation
                                 is      given
                                          1 and the
                                    the Cholesky     assumed    pathofofΣthe
                                                3 isdecomposition
                                                     that the reduced-form    rest
                                                                            VAR
                                                                           and      of
                                                                                Qis is athe
                                                                                     a mere variables).
                                                                                         n ×statistical   As
                                                                                                        model,
                                                                                              n orthogonal
for which estimation is possible. Conversely, the structural augmentation makes the model economically
interpretableinbut
explained            Antolín-Díaz
                        not feasible for    et estimation.
                                                  al. (2021),These
                                                                the structural   identification
                                                                     types of models               of D does
                                                                                       are the workhorse        not playmacroe-
                                                                                                          for empirical   a role
conomics since their introduction by Sims (1980).
in 12how
       There  theis an
                    conditional        forecasts
                       ongoing discussion                arehow
                                                     about    constructed
                                                                       6 using
                                                                 appropriate         this approach.
                                                                             this identification        However,
                                                                                                 strategy is, see Frystructural
                                                                                                                      and Pagan
(2011), Baumeister and Hamilton (2015), Uhlig (2017), Inoue and Kilian (2020). Yet for the purpose of our
identification
analysis     this 13
  BANCO DE ESPAÑA
                       still helpsscheme
                   identification        to gain
                      DOCUMENTO OCASIONAL N.º 2114
                                                         insights
                                                   is flexible and on  why we observe this forecasting path for the
                                                                   well-established.

unconditioned variable in the context of a “what if” scenario. Therefore, for the benchmark
                                              7
model we run the central forecasts based on the technical assumptions and obtain the baseline
forecasts in terms of sequences of observables, as described by Waggoner and Zha (1999). In

particular, the conditional forecasts when using this technique describe the most likely future
path of the unconditioned variable given conditions imposed for the rest of variables (i.e., the
likely future path of GDP growth given the assumed path of the rest of the variables). As
explained in Antolín-Díaz et al. (2021), the structural identification of D does not play a role
established by Ai = DDi , C = DK, εt = Dηt and Σ = DΓD⊤ , with D = D0−1 . To recover
in how the conditional forecasts are constructed using this approach.           However,  structural
established
the          by model
    structural  Ai = DDfromi , its
                               C=  reduced-form
                                     DK, εt = Dη    and Σ = DΓD
                                                ort disentangle       , with
                                                                ηt from
                                                                    ⊤
                                                                         εt , one D0−1 .toToadopt
                                                                              D =needs        recover
                                                                                                   an
identification still helps to gain insights on why we observe this forecasting path for the
the structural strategy
identification  model from     its reduced-form
                         to restrict            or disentangle
                                      the contemporaneous       ηt from
                                                            matrix   D. εt , one needs to adopt an
unconditioned variable in the context of a “what if” scenario. Therefore, for the benchmark
identification strategy to restrict the contemporaneous matrix D.
model we run the central forecasts based on the technical assumptions and obtain the baseline
2.3        Conditional Forecasts
projection   without adopting
2.3 Conditional                 any specific structural identification. Contrary, for the satellite
                           Forecasts
Note that the baseline projection and the risk scenarios are carried out through conditional
models used for simulating risk scenarios, it makes sense to identify structural shocks to gain
Note  thatinthe
forecasts        baseline
              terms       projection
                    of sequences     and the risk as
                                  of observables,  scenarios areby
                                                     described    carried out through
                                                                    Waggoner   and Zhaconditional
                                                                                        (1999). In
additional insights regarding the impact of the scenarios on the baseline projections.
forecasts
particular,inthe
              terms of sequences
                 conditional      of observables,
                             forecasts when usingasthis
                                                     described  by describe
                                                        technique   Waggonertheand Zhalikely
                                                                                most    (1999).  In
                                                                                             future
particular,
path of the the conditional variable
            unconditioned   forecastsgiven
                                      whenconditions
                                           using this imposed
                                                       techniquefordescribe
                                                                    the restthe most likely
                                                                             of variables    future
                                                                                          (i.e., the
2.4        Satellite Models
path
likelyoffuture
          the unconditioned
                  path of GDPvariablegrowth given conditions
                                                       the assumed       imposed
                                                                             path of forthe
                                                                                         therest
                                                                                              restofof the
                                                                                                        variables    (i.e., the
                                                                                                             variables).     As
In the spirit of Leiva-Leon (2017) we partially set-identify the satellite models using sign
likely  future
explained         path of GDPetgrowth
             in Antolín-Díaz                    giventhe
                                       al. (2021),     thestructural
                                                              assumed identification
                                                                             path of the rest of Dofdoes
                                                                                                       the not
                                                                                                             variables).
                                                                                                                  play a roleAs
restrictions. For conducting the sign restriction identification, one needs to focus on εt =
                12
explained
in how theinconditional
                 Antolín-Díaz       et al. (2021),
                                 forecasts           the structural
                                              are constructed         using identification
                                                                               this approach. of D However,
                                                                                                     does not play       a role
                                                                                                                   structural
Dηt to restrict the contemporaneous impact matrix D. For the case of sign-identified models
in  how the conditional
identification     still helpsforecasts       are constructed
                                  to gain insights      on why using           this approach.
                                                                       we observe                   However,
                                                                                        this forecasting       pathstructural
                                                                                                                       for the
we have D = P Q, where P is the Cholesky decomposition of Σ and Q is a n × n orthogonal
identification
unconditionedstill        helpsintothe
                     variable         gain    insights
                                         context    of aon    whyif”
                                                          “what        wescenario.
                                                                             observe Therefore,
                                                                                        this forecasting
                                                                                                      for thepath      for the
                                                                                                                  benchmark
interpretable   but  not feasible
                             ⊤ for estimation. These types of models are the workhorse for empirical macroe-
matrix such that QQ = In , with In being the n-dimensional identity matrix. Then, to
unconditioned
model wesince
conomics    runtheir variable
                   the central  inforecasts
                        introductionthebycontext
                                           Simsbasedofon
                                                       a “what
                                                  (1980).            if” scenario.
                                                          the technical                 Therefore,
                                                                               assumptions            for thethe
                                                                                                and obtain        benchmark
                                                                                                                     baseline
   12
      There is  an  ongoing  discussion   about  how  appropriate      this  identification
achieve identification rewrite the vector of structural impulse responses as Ξ = f (A, Σ,   strategy   is, see Fry  and  Pagan
                                                                                                                            Q),
model
(2011),  we run
projection
        Baumeister theand
              without  central
                          adoptingforecasts
                            Hamilton   any
                                       (2015), based
                                                 Uhligon
                                              specific    the technical
                                                       structural
                                                       (2017),             andassumptions
                                                                 Inoueidentification.           and
                                                                                            Contrary,
                                                                                Kilian (2020).        obtain
                                                                                                Yet for          the baseline
                                                                                                            for purpose
                                                                                                           the        satellite
                                                                                                                         of our
analysisfthis
where          identification
          (·) is  a non-linear scheme   is flexible
                                   function,    A=  and
                                                      (Awell-established.
                                                          1 , A2 , . . . , An ) contains the coefficient matrices, Σ
projection
models used   without     adoptingrisk
                 for simulating        anyscenarios,
                                              specific structural
                                                        it makes sense   identification.
                                                                               to identifyContrary,
                                                                                             structuralfor       the satellite
                                                                                                             shocks    to gain
is the covariance of reduced-form errors, and Q is the matrix from which to obtain candidate
models
additionalused   for simulating
              insights    regarding  risk
                                        thescenarios,
                                              impact of it the
                                                            makes      sense toonidentify
                                                              7 scenarios                    structural
                                                                                     the baseline            shocks to gain
                                                                                                      projections.
draws that satisfy the imposed sign restrictions. Refer to Kilian and Lütkepohl (2017) for
additional insights regarding the impact of the scenarios on the baseline projections.
an extensive discussion in the identification and estimation of sign-restricted models and to
2.4        Satellite Models
Arias
2.4 etSatellite
          al. (2018) for     the practical implementation we use for this class of models.
                         Models
In the spirit of Leiva-Leon (2017) we partially set-identify the satellite models using sign
    Moving to the details of the specification of the satellite models, each one of them contains
In  the  spirit12ofFor
restrictions.        Leiva-Leon
                        conducting  (2017)   we partially
                                        the sign  restrictionset-identify  the satellite
                                                               identification,  one needsmodels    using
                                                                                            to focus  on εsign
                                                                                                           t =
a set of core variables shared across all satellite models and then additional variables included
Dηt to restrict For
restrictions.  12
                        conducting the sign
                   the contemporaneous            restriction
                                               impact  matrixidentification,
                                                                D. For the case oneofneeds  to focus on
                                                                                      sign-identified   models
                                                                                                          εt =
explicitly for the risk scenario. The core variables are GDP growth, inflation, and interest
we   to restrict
Dηthave   D = Pthe      contemporaneous
                    Q, where                   impactdecomposition
                                P is the Cholesky      matrix D. For of  theΣcase
                                                                               and of
                                                                                   Q sign-identified    models
                                                                                       is a n × n orthogonal
rates. As is common in the literature, these three variables are used to identify demand, cost-
we  have D =
interpretable butPnot   where P
                    Q, feasible forisestimation.
                                       the Cholesky
                                                 Thesedecomposition     of Σ
                                                       types of models are  theand Q is afor
                                                                                workhorse   n×  n orthogonal
                                                                                              empirical macroe-
push,  and
conomics     monetary
          since            policy shocks.
                 their introduction   by SimsThen,
                                              (1980).we augment this core setup with scenario-specific
interpretable
    12
       There is but  not feasible
                 an ongoing        for estimation.
                              discussion  about howThese   types ofthis
                                                      appropriate   models    are the workhorse
                                                                         identification           forsee
                                                                                         strategy is,  empirical
                                                                                                          Fry andmacroe-
                                                                                                                  Pagan
variables
conomics
(2011),      to identify
           since  theirand
         Baumeister          additional
                         introduction
                            Hamilton    by structural
                                           SimsUhlig
                                        (2015),  (1980).shocks.
                                                       (2017),    Weand
                                                               Inoue     specify
                                                                             Kilian the  following
                                                                                     (2020). Yet for satellite  models:
                                                                                                      the purpose of our
    12
       There
analysis  thisisidentification
                 an ongoing discussion
                               scheme isabout    how
                                           flexible   appropriate
                                                    and            this identification strategy is, see Fry and Pagan
                                                        well-established.
(i)  the Baumeister
(2011),  external model        with y(2015),
                       and Hamilton              Uhlig
                                        external,t     (2017),tInoue
                                                    = (EXD     , GDPand      Kilian
                                                                        t , IN       (2020).
                                                                               Ft , IN         where
                                                                                        Tt )⊤Yet for thewepurpose
                                                                                                            identify an
                                                                                                                  of our
analysis this identification scheme is flexible and well-established.
external shock,
           14
  BANCO DE ESPAÑA
                                          7 ycommodity,t = (OILt , GDPt , IN Ft , IN Tt )⊤
                (ii) the commodity model with
                    DOCUMENTO OCASIONAL N.º 2114

                                          7 the uncertainty model with yuncertainty,t =
where we identify a commodity shock, and (iii)

(GDPt , IN Ft , EM Bt , EP Ut , IN Tt )⊤ where we identify financial risk and economic policy risk
explicitly for the risk scenario. The core variables are GDP growth, inflation, and interest
rates. As is common in the literature, these three variables are used to identify demand, cost-
push, and monetary policy shocks. Then, we augment this core setup with scenario-specific
variables to identify additional structural shocks. We specify the following satellite models:

(i) the external model with yexternal,t = (EXDt , GDPt , IN Ft , IN Tt )⊤ where we identify an
external shock, (ii) the commodity model with ycommodity,t = (OILt , GDPt , IN Ft , IN Tt )⊤
where we identify a commodity shock, and (iii) the uncertainty model with yuncertainty,t =
(GDPt , IN Ft , EM Bt , EP Ut , IN Tt )⊤ where we identify financial risk and economic policy risk
shocks. In the fourth scenario concerning the long-term effects of output, we use (iv) the

potential output model which has the same ten variables as the benchmark model ypotential,t =
yt . Given that in this particular scenario we are concerned with deviations from the steady-
state and not in deviations from the technical assumptions, we implement an alternative

modelling strategy detailed later.
    Following the literature described in Leiva-Leon (2017) we establish the structural iden-
tification schemes for the satellite models (i) - (iii):

    External:                                                                            
                                                                   ∗   ∗
                                                                       ∗   ηexternal,t 
                                          εexd,t  
                                                       +
                                                                                    
                                          εgdp,t  +             + − −   ηdemand,t 
                                                                                    
                                                  =                                 .            (4)
                                          ε                            η            
                                           inf,t   ∗            + + −  cost−push,t 
                                                                                    
                                            εint,t     ∗             8
                                                                   + + +    ηmonetary,t

    Commodity:                                                                           
                                          εoil,t  +             ∗   ∗
                                                                   ∗  ηcommodity,t
                                                                                     
                                                                                
                                         εgdp,t  +          + − −   ηdemand,t 
                                                                                
                                                 =                              .                (5)
                                                  
                                                               + + −  ηcost−push,t 
                                                                      
                                         εinf,t  +                                
                                                                                
                                           εint,t     ∗        + + +     ηmonetary,t

    Uncertainty:
                                                                                             
                                        ε          +           − − − −                η
                                       gdp,t                                    demand,t 
                                                                                             
                                       εinf,t  +            + ∗         ∗   −  ηcost−push,t 
                                                                                             
                                                                                             
                                      ε        
                                       emb,t  =  ∗          ∗ + ∗           ∗   ηf in−risk,t 
                                                                                  
                                                                                                  .   (6)
                                                                                             
                                                                                             
                                       εepu,t   ∗           ∗       ∗ +     ∗   ηpol−risk,t 
                                                                                             
                                        εint,t     +           + ∗         ∗   +     ηmonetary,t

    Each entry in the D matrix describes how the responses to the structural shocks will
                   15
be restricted in relation to the observables. That is, the candidate draws from Q have to
 BANCO DE ESPAÑA        DOCUMENTO OCASIONAL N.º 2114

satisfy the positive and negative sign restrictions in order to be accepted and they are then
epu,t                                  pol−risk,t
                                                                                      
                                     εint,t              + + ∗    ∗ +        ηmonetary,t

    Each entry in the D matrix describes how the responses to the structural shocks will
be restricted in relation to the observables. That is, the candidate draws from Q have to
satisfy the positive and negative sign restrictions in order to be accepted and they are then
2.5        Auxiliary Models
used to obtain Ξ from the posterior distribution. The symbol “*” denotes that the entry
Lastly,
in      for theisscenario
   the matrix             on the long-term
                  left unrestricted.        effects
                                     With these     on output we
                                                 sign-identified    use the
                                                                 satellite   potential
                                                                           models,     output
                                                                                   we run the
satelliteforecasts
central   model which   is based
                   following the on an alternative
                                 technical         BVARand
                                           assumptions   model. Specifically,
                                                           the scenario       since based
                                                                        forecasts    our goal
                                                                                          on
is to impose
deviations    a different
           from           steady-state
                 the technical         than for
                               assumptions   thesome
                                                 one from the baseline
                                                     variables.         projection
                                                                The difference     we decide
                                                                               between these
to depart
two       from
    forecasts   the standard
              results in the netBVAR
                                 effect described above
                                        that is added to and use the mean-adjusted
                                                         the baseline projection and BVAR  of
                                                                                     measures
Villani
the     (2009).
    impact      In this
            of the risk alternative
                        scenario. representation of the model, the unconditional mean of the
vector of variables is E(yt ) = µ, where µ is an n × 1 vector of constants with the steady-state
2.5    Auxiliary
values.13            Models
          Hence, we can now include information on the steady-state through the prior mean
of µ. for the scenario on the long-term effects on output we use the potential output
Lastly,
                                              9
satellite model which is based on an alternativeand
    Next,  we obtain potential output for Brazil    Mexico
                                                  BVAR     usingSpecifically,
                                                        model.   an auxiliarysince
                                                                              model.
                                                                                   ourUsing
                                                                                       goal
historical
is         data,
   to impose     we fit a calibrated
              a different            Cobb-Douglas
                           steady-state           production
                                        than the one from thefunction
                                                               baselineand apply theweHodrick-
                                                                        projection     decide
Prescott
to depart(HP)
          fromfilter
                the with smoothing
                     standard BVARparameter
                                   describedλabove   to the
                                                   and
                                              = 1600    use production factors toBVAR
                                                             the mean-adjusted    compute
                                                                                       of
the long-run
Villani      trend
        (2009).     of output.
                In this         As explained
                        alternative           by Tóth
                                    representation     (2021),
                                                   of the      this
                                                          model, theisunconditional
                                                                       a common approach
                                                                                    mean ofused
                                                                                            the
by international
vector of variablesorganizations
                     is E(yt ) = µ,to obtain
                                    where µ isa an
                                                measure   of potential
                                                   n × 1 vector        output.
                                                                of constants   Assuming
                                                                             with         that the
                                                                                  the steady-state
time-series
values.13   considered
          Hence, we cancan
                        nowbeinclude
                              decomposed   into a on
                                     information  cycle
                                                     theand  a trend component,
                                                         steady-state through thewe specify
                                                                                  prior meana
production
of µ.      function with constant returns to scale:

    Next, we obtain potential output for Brazil and Mexico using an auxiliary model. Using
                                       Y ∗ = A∗ K ∗α L∗1−α ,                             (7)
historical data, we fit a calibrated Cobb-Douglas production function and apply the Hodrick-
Prescott (HP) filter with smoothing parameter λ = 1600 to the production factors to compute
where the asterisk denotes the trend component of a variable, and Yt refers to output, At to
the long-run trend of output. As explained by Tóth (2021), this is a common approach used
Total Factor Productivity (TFP), Kt to capital, and Lt to labor. The parameter α is the
by international organizations to obtain a measure of potential output. Assuming that the
share of capital in output.
time-series considered can be decomposed into a cycle and a trend component, we specify a
    We first construct the capital series using the perpetual inventory method, that is, iter-
production function with constant returns to scale:
atively applying the law of motion of capital:

                                                       Y ∗ = A∗ K ∗α L∗1−α ,                            (7)
                                                  Kt = (1 − δ)Kt−1 + It , t ≥ 1,                        (8)
   13
        This relation is straight forward because the only exogenous component of our model is the vector of
where  theC,asterisk
constants             denotes
             for the full        the oftrend
                          derivation          component
                                         the model refer to of a variable,
                                                            Villani (2009). and Yt refers to output, At to

Total Factor Productivity (TFP), Kt to capital, and Lt to labor. The parameter α is the
           16                             10
share of capital in output.
 BANCO DE ESPAÑA   DOCUMENTO OCASIONAL N.º 2114

    We first construct the capital series using the perpetual inventory method, that is, iter-
Y ∗ = A∗ K ∗α L∗1−α ,                   (7)

where the asterisk denotes the trend component of a variable, and Yt refers to output, At to
Total Factor Productivity (TFP), Kt to capital, and Lt to labor. The parameter α is the
share of capital in output.

     We first construct the capital series using the perpetual inventory method, that is, iter-
atively applying the law of motion of capital:

                                                       Kt = (1 − δ)Kt−1 + It ,           t ≥ 1,      (8)
   13
     This relation is straight forward because the only exogenous component of our model is the vector of
constants C, for the full derivation of the model refer to Villani (2009).
where It denotes investment and δ is the depreciation rate of capital. We initialize K0 in (8)
with the pre-sample historical average. We compute
                                            10     TFP by the Solow residual:

                                                                          Yt
                                                               At =             .                    (9)
                                                                       Ktα L1−α
                                                                            t

     The series for the labor input is observable, but we need to pin down values for α and δ to
determine the evolution of capital and TFP. Following the common practice in neoclassical

growth models we calibrate these parameters by computing the averages of the right-hand
side terms in the following equations:

                                                                          w t Lt
                                                               α=1−              ,                  (10)
                                                                           Yt
                                                                      It 1
                                                                        ( − 1)
                                                                                                    (11)
                                                                      Yt β
                                                               δ=                    ,
                                                                     α YItt
                                                                    1
                                                               β=          ,                        (12)
                                                                  1 + rt

where wt is the real wage rate and rt is the real rental rate of capital. For the forecasting
periods, we iterate forward the series of each factor input using long-term growth rates

proxied by historical averages. Subsequently, we apply the HP filter to the factor input series
and substitute their trend components into the Cobb-Douglas production function (7). In
this way, we obtain potential output Y ∗ for both countries over the historical and forecasting
periods.
     Using this auxiliary model, we calculate steady-states as the average of potential output
growth rates over all periods. To compute an alternative steady-state from a simulated
scenario, we assume that factor inputs evolve at different long-term growth rates than the
 BANCO DE ESPAÑA   17   DOCUMENTO OCASIONAL N.º 2114

ones assumed initially. This results in different trend components of the factor inputs and
therefore yields an alternative potential output series. The differences between these averages
Using this auxiliary model, we calculate steady-states as the average of potential output

growth rates over all periods. To compute an alternative steady-state from a simulated
scenario, we assume that factor inputs evolve at different long-term growth rates than the
ones assumed initially. This results in different trend components of the factor inputs and
therefore yields an alternative potential output series. The differences between these averages

2.6   Data
determine the deviation of the steady-state from the baseline projection. We introduce it

into the mean-adjusted BVAR through alternative priors for µ.
We use quarterly data from 2000Q1 to 2020Q4, but the estimation sample runs until 2019Q4
and the year 2020 is included as conditional paths
                                             11    for the forecasting exercises. We do so to
2.6       Data
avoid problems in the estimation process and the stability of the parameters in the model
We
due use quarterly
    to outliers in data
                   mostfrom  2000Q1
                        variables    to 2020Q4,
                                  during        but the period.
                                         the COVID-19   estimation
                                                                14  sample
                                                                   Given   runs
                                                                         that theuntil
                                                                                  focus2019Q4
                                                                                         of the
and theis year
paper           2020 is included
           to illustrate         as conditional
                         the functionalities     paths
                                             of the    for the
                                                    toolkit andforecasting exercises.
                                                                 the simulation       Wescenarios
                                                                                 of risk do so to

avoid problems
rather         in the estimation
       than accurately forecastingprocess and thecurrent
                                   GDP during     stability of thethis
                                                          times,    parameters
                                                                       approachinisthe
                                                                                    themodel
                                                                                        most
due to outliers
appealing       in most
          for our       variables during
                   applications.  Yet in the
                                         our COVID-19     reports ofGiven
                                             half-yearly period.
                                                                 14
                                                                     Bancothat
                                                                            dethe focus (2020)
                                                                               España   of the

paper is to de
and Banco   illustrate
                Españathe functionalities
                       (2021),            of the
                               we explicitly  dealtoolkit and current
                                                    with this the simulation of risk there
                                                                      issue because  scenarios
                                                                                           our
rather
growth than  accurately
        projections      forecasting
                    reflect our most GDP  during
                                     updated     current
                                             stance on thetimes,
                                                            futurethis approach
                                                                   evolution     is the
                                                                             of the     most
                                                                                    Brazilian
appealing for economies.
and Mexican    our applications. Yet on
                          For details in how
                                         our half-yearly
                                             we do this, reports
                                                         refer to of
                                                                  theBanco de España (2020)
                                                                      reports.
andData
    Banco de España
        included have(2021), we explicitly
                      the following        dealWe
                                    features.   with thisseasonally
                                                  took     current issue because
                                                                    adjusted real there
                                                                                   GDP,our
                                                                                        as
growth projections
published          reflect ourstatistics
          by the respective     most updated
                                         offices.stance onseasonally
                                                   To get  the future adjusted
                                                                       evolutioncore
                                                                                 of the
                                                                                     CPIBrazilian
                                                                                          we use
and MexicanX-13-ARIMA-SEATS
the method  economies. For detailsfrom
                                    on how we do this,
                                        JDemetra+. 15 refer to the reports.
                                                       For other high-frequency variables,
    Data
daily    includeddata
      or monthly  haveare
                       theaveraged
                            followingtofeatures. We took
                                        get quarterly series.seasonally adjusted
                                                               The growth        realexpressed
                                                                           rates are  GDP, as

published by the respective
as quarter-on-quarter       statistics
                      percentages.     offices. we
                                    Moreover,   To test
                                                   get seasonally  adjusted
                                                        for stationarity usingcore
                                                                                theCPI we use
                                                                                    augmented
the method X-13-ARIMA-SEATS
Dickey-Fuller                   from JDemetra+.15 For other
              (ADF) and Kwiatkowski-Phillips-Schmidt-Shin     high-frequency
                                                          (KPSS)               variables,
                                                                 tests and in the latter,
daily
there or  monthlyempirical
      is enough   data areevidence
                           averagedtotoreject
                                         get quarterly series.ofThe
                                              the hypothesis     unitgrowth  rates
                                                                      roots at a 5%aresignificance
                                                                                        expressed
as quarter-on-quarter percentages. Moreover, we test for stationarity using the augmented
level.
Dickey-Fuller
   Our data is(ADF) and Kwiatkowski-Phillips-Schmidt-Shin
                downloaded from international sources as well(KPSS)  tests sources.
                                                              as national   and in the latter,
                                                                                    Starting
therethe
with  is enough  empirical evidence
          global variables,           to reject
                            for the foreign     the hypothesis
                                             demand,           of unit
                                                      we use real      rootsofatgoods
                                                                  imports        a 5%and
                                                                                      significance
                                                                                          services
level.
from national sources. The bilateral exports data to construct the weights in the foreign
   Our data
demand      is downloaded
       measure   come fromfrom  international
                           the IMF’s          sources
                                      Direction       as well
                                                 of Trade     as national
                                                          Statistics      sources.
                                                                     (DOTS).   We Starting
                                                                                   consider
with the global
the main        variables,for
         trade partners     forboth
                                the countries:
                                    foreign demand,  we we
                                               in Brazil usetake
                                                             real the
                                                                   imports of goods
                                                                      US, Euro  Area,and
                                                                                      andservices
                                                                                           China
from
   14 national sources. The bilateral exports data to construct the weights in the foreign
     For a more thorough treatment on how to perform estimation and forecasts with VARs in the context
of the COVID-19 pandemic see Lenza and Primiceri (2020) and Primiceri and Tambalotti (2020).
demand
    15
       This measure
            software iscome
                        a toolfrom   the IMF’s
                               specifically       Direction
                                            designed          of Trade
                                                     for the seasonal   Statisticsof (DOTS).
                                                                      adjustment      time-series We
                                                                                                  and consider
                                                                                                      has been
officially recommended by the European Commission. For more details visit the website here.
the main trade partners for both countries: in Brazil we take the US, Euro Area, and China
   14
       For a more thorough treatment on how to perform estimation and forecasts with VARs in the context
               18 DOCUMENTO OCASIONAL N.º 2114
 BANCO DE ESPAÑA
of the COVID-19 pandemic see Lenza and Primiceri (2020) and Primiceri and Tambalotti (2020).
    15                                                 12
       This software is a tool specifically designed for the seasonal adjustment of time-series and has been
officially recommended by the European Commission. For more details visit the website here.
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