Data Analysis of Shipment for Textiles and Apparel from Logistics Warehouse to Store Considering Disposal Risk - MDPI

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sustainability

Article
Data Analysis of Shipment for Textiles and Apparel
from Logistics Warehouse to Store Considering
Disposal Risk
Rina Tanaka 1 , Aya Ishigaki 1, * , Tomomichi Suzuki 1 , Masato Hamada 2 and Wataru Kawai 2
 1    Industrial Administration, Tokyo University of Science, Noda, Chiba 278-8510, Japan;
      7418519@ed.tus.ac.jp (R.T.); szk@rs.tus.ac.jp (T.S.)
 2    Data-Chef Co., Ltd., Koto-ku, Tokyo 135-0004, Japan; m.hamada@data-chef.co.jp (M.H.);
      w.kawai@data-chef.co.jp (W.K.)
 *    Correspondence: ishigaki@rs.noda.tus.ac.jp; Tel.: +81-4-7124-1501
                                                                                                     
 Received: 24 November 2018; Accepted: 2 January 2019; Published: 7 January 2019                     

 Abstract: Given the rapid diversification of products in the textile and apparel industry, manufacturers
 face significant new challenges in production. The life cycle of apparel products has contracted and is
 now, generally, a several-week season, during which time a majority of products are supposed to be
 sold. Products that do not sell well may be sold at a price lower than the fixed price, and products
 that do not sell at all within the sales period may eventually become forced disposal. This creates
 long-term management and environmental problems. In practice, shipping personnel determine
 when to ship products to stores after reviewing product sales information. However, they may not
 schedule or structure these shipments properly because they cannot effectively monitor sales for a
 large number of products. In this paper, shipment is considered to reduce the risk of product disposal
 on the premise of selling at a fixed price. Although shipment quantities are determined by various
 factors, we only consider the change in inventory at the logistics warehouse, since it is difficult to
 incorporate all factors into the analysis. From cluster analysis, it is found that shipping personnel
 should recognize a policy to sell products gradually over time. Furthermore, to reduce the risk of
 disposal, we forecast the inventory from conditional probability and are able to extract products out
 of a standard grouping using past data.

 Keywords: apparel products; supply chain management; quick response; clustering; forecasting;
 sale at fixed price

1. Introduction
     Environmental problems such as global warming and water shortages along with the expansion
of social disparities from globalization not only remain unsolved in the world, they continue to
escalate. Thus, the need for companies to play significant roles in shaping sustainable societies is
also increasing [1]. A society can be considered sustainable from three perspectives—environmental,
societal, and economic [2]; these are often referred to as the triple bottom line or 3BL [3]. Companies
must consider the impact of their business activities on the 3BL and establish long-term corporate
strategies to minimize adverse impacts in any of these dimensions. By employing this perspective
in supply chain management, in particular, companies are more likely to achieve sustainability [4],
which in turn can enhance a company’s competitive advantage [5]. Even in the textile and apparel
industry—which is subject to the vagaries of fashion and, thus, characterized by short product life
cycles—companies are focusing more on sustainability as globalization progresses [6]. In this industry,
the emphasis in sustainable supply chain management is placed on effective risk management.

Sustainability 2019, 11, 259; doi:10.3390/su11010259                      www.mdpi.com/journal/sustainability
Sustainability 2019, 11, 259                                                                         2 of 14

     In a textile and apparel supply chain, a company’s factories manufacture products according
to a designated production plan. Afterwards, via logistics warehouses, the company ships finished
products to stores. At the start of a sales period, a quantity of products is made available at stores based
on the production plan. At the end of the sales period, it is hoped that inventories of stores and the
logistics warehouse will have harmonized with the production plan as well as with customer demand.
In practice, however, customer demand often deviates from what is anticipated in the production
plan, and a surplus or shortage results. This is because of the long lead times before a sales period [7]
and because apparel products are seasonal, that is, usually only one season. Further, in the textile
and apparel industry, the logistics warehouses serve as stock points, and therefore, decisions about
shipments to logistics warehouses are crucial [8].
     In recent years, as customer needs and preferences have proliferated, textile and apparel
products have been made available in an ever-widening range of colors and sizes [9]. Moreover,
an increasing number of manufacturers also sell more general apparel products—such as bags, shoes,
and accessories—in addition to clothes [10]. Because of these trends, leading to modifications in the
design of apparel products every season, demand uncertainty in the industry is large compared to
that for industries with more stable products, such as office supplies, or furniture. In other words,
every season there are new apparel products with very short life cycles [9]. Therefore, it is difficult to
forecast when and which products will be sold at any given time [11].
     Many factors are at play in textile and apparel supply chains. When shipping products from
the production plants to the logistics warehouse, timing and quantities are determined in advance.
On the other hand, when shipping from the logistics warehouse to stores, timing and quantities can
be modified in accordance with customer demand by taking into account actual sales information.
The earlier that shipments are sent from the logistics warehouse, the higher is the possibility that
inventory at the stores will become excessive, such that unsold products will eventually be returned to
the logistics warehouse and discarded. Inventory space in a store may also be quite limited, resulting
in the need to return or dispose of excess product. In contrast, when shipments from the logistics
warehouse are delayed, stores can experience shortages and, as a result, lose opportunities for sales.
In addition, because of long lead times before sales seasons, trends may have already have shifted
by the time the season arrives, with the result that product designs will have become unsuitable
for selling.
     Shipping personnel are responsible for controlling inventory by determining shipments (timing
and quantities) from the logistics warehouse to stores. Normally, these personnel rely on signals from
stores when deciding if additional shipments are necessary [12]. Because of the range of products and
frequency of shipments, however, it is difficult for them to efficiently and accurately track all sales
information. These shortcomings can result in excess product, the proper disposal of which has become
a significant environmental problem. The textile and apparel industry is the second largest industry in
the world; as such, it can have an enormous impact on the global environment [13], particularly since
waste is generated at every stage of in the apparel manufacturing process [14].
     In sum, the disposal of excess product within the apparel industry is an increasing threat to the
environment [15]. To minimize the quantity of unsold product, manufacturers should more carefully
consider customer demand when making production decisions. In this way, they can fulfill their role
in helping to build a sustainable society, at least from an environmental perspective. From an economic
perspective, manufacturers face another related challenge: anticipating a disposal problem, they may
significantly lower the price of products to try to sell more product and, hence, mitigate the challenge
of disposal. An increase in the number of unsold products at the end of a sales cycle, then, would lead
to an increase in the number of products whose price was discounted by the company. If this cycle
were to continue, profits would inevitably decline and sustaining the business over the long term
would become more difficult. To prevent problems such as this in the economic dimension, companies
would need to increase or at least maintain the number of products sold at a fixed price.
Sustainability 2019, 11, 259                                                                        3 of 14

     On the premise of selling at a fixed price, we consider the timing of shipping as a method to
reduce waste risk due to unsold inventory in this study. Initially, the sales scenario of the products
that the shipping personnel need to monitor is restricted. Next, in consideration of the need to sell
these products at a fixed price, personnel forecast the inventory ratio in the sales period and consider
shipping timing in order to reduce the disposal risk.

2. Literature Review
      Unsustainable and unregulated production and consumption are contributing to the degradation
of the global environment [16]. Proper monitoring and analysis in the textile and apparel supply chain
is necessary to minimize its environmental impact [17]. A literature review on the apparel supply
chain is as follows.
      The sustainability of the textile and apparel supply chain has two aspects: environment
sustainability such as reduction of unsold products and economic sustainability that improves return
on investment (ROI) [18]. With environment sustainability, manufacturers are required to manage
resource procurement, inventory, waste treatment, and transport efficiently. On the other hand,
with economic sustainability, manufacturers are required to increase the number of products sold
at regular price and have large sales. Caniato et al. investigated large and small companies on the
problem of environment sustainability in fashion supply chain [19]. As a result, large companies tend
to focus more on improving products and processes, and small and medium companies tend to rebuild
supply chains. Choi and Chiu proposed the mean-downside-risk (MDR) and mean-variance (MV)
newsvendor model considering both environment sustainability and economic sustainability [20].
      Brun and Castelli explored specific factors or product characteristics that promote competition in
the fashion industry [21]. Čiarnienė and Vienažindienė identified key features of the modern fashion
industry and developed a time efficient supply chain model [22]. Mehrjoo and Pasek described the
structure of the apparel supply chain using system dynamics and quantitatively evaluated its risk [23].
Patil et al. developed a mathematical model to evaluate procurement, shipping, and markdown plans
for new short-term life cycle products considering discounts associated with large-scale purchase and
bulk transport [24].
      In order for the shipping personnel to recognize when to send additional shipments, they rely
on signals that indicate when products have been sold at stores. This system is known as Quick
Response (QR), and it has demand-driven characteristics. Quick Response reduces lead time and
allows shippers to quickly respond to market needs [25]. It was first implemented in the US apparel
industry in the middle 1980s as a strategy for global response [26] and, since then, its use has spread to
other industries. It was designed to be an inventory management strategy that was based on sharing
information among supply chain agents [27]. By using a QR strategy, lead time is shorter because the
shipping personnel can better forecast customer demand and subsequently modify the production
plan [25]. In basic QR, a retailer sends point of sale (POS) data to its supplier, who then uses this
information to improve demand forecasting [28]. Tsukagoshi et al. proposed using a QR inventory
management strategy of introducing a monitoring period prior to the normal sales period in cases for
which replenishment lead time is short compared to the sales period. They found that this approach
reduced total shortage costs [29]. Tanaka et al. analyzed shipping data on the premise of selling
at a fixed price [8]. They considered the risk of running out of stock but not the risk of disposal of
unsold products.
      In the apparel market, sales forecasting plays an increasingly important role in decision support
systems for market competition and globalization [30]. Thomassey explained specific constraints and
needs related to supply chain and sales forecasts in the textile apparel industry [31]. In a large set of
SKUs and two consecutive sales seasons, Mostard et al. compared the accuracy of three quantitative
forecasting methods based on advance demand information [11]. Fan et al. proposed a prediction
model combining the Bass/Norton model and the sentiment analysis method [32].
Sustainability 2019, 11, 259                                                                                                               4 of 14

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3. Status of Products
      3. Status
      In  general, of Products
                       a manufacturer       stores new products in one logistics warehouse for each supply chain.
       Sustainability 2019, 11 FOR PEER REVIEW                                                                                     4
Also, a range       of products
            In general,              can bestores
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                                                   Figure 1. 1.Conceptual
                                                     Figure     Conceptual Diagram  ofSupply
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        should increase
                  0.80
                   1.00
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                  0.70
                   0.90
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                      Inventory

                  0.50
                   0.70                                                                                             Product 1
                  0.40
                   0.60                                                                                             Product 2
                Inventory

                  0.30
                   0.50                                                                                             Product 1
                                                                                                                    Product 3
                  0.20
                   0.40                                                                                             Product 2
                  0.10
                   0.30
                  0.00                                                                                               Product 3
                   0.20
                   0.10 0    1     2     3     4      5      6      7    8      9
                                        0.00                              Week
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                                                         Figure 2.3 Example
                                                                        4 of Inventory
                                                                             5      6 Ratio
                                                                                          7 Change.
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                                                          Figure
                                                       Figure 2. 2. Exampleof
                                                                 Example    ofInventory
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                                                                                         RatioChange.
                                                                                               Change.
Sustainability 2019, 11, 259                                                                      5 of 14
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                        500
                        450
                        400
                        350
                        300
            Frequency

                        250
                        200
                        150
                        100
                         50
                         0
                              0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
                                                   Inventory Ratio
                                  Figure3.3.Histogram
                                 Figure     Histogramof
                                                      ofInventory
                                                         InventoryRatio
                                                                  Ratioin
                                                                        inNinth
                                                                          NinthWeek.
                                                                                Week.
4. Methods
 4. Methods
      In this paper, we assume the supply chain as shown in the Figure 1. Since the sales cycle of the
       In this paper, we assume the supply chain as shown in the Figure 1. Since the sales cycle of the
textile and apparel supply chain is one week [33], we perform our analysis using weekly data. The data
 textile and apparel supply chain is one week [33], we perform our analysis using weekly data. The
used in this paper is collected in the logistics warehouse.
 data used in this paper is collected in the logistics warehouse.
4.1. Assumptions, Parameters, and Variables
 4.1. Assumptions, Parameters, and Variables
      In this paper, the following assumptions, parameters, and variables are used. The parameters and
       In this
variables  are paper,  the in
               described    following
                              subsequent assumptions,
                                             sections. parameters, and variables are used. The parameters
 and variables are described in subsequent sections.
Assumptions:
 Assumptions:
•     Products are sold in the same period
 •     Products are sold in the same period
•     The total arrival quantity of each product is known
 •     The total arrival quantity of each product is known
•     Product movement among stores is not considered
 •     Product movement among stores is not considered
•• The Theperiod
            periodininwhich
                       whichproducts
                               productsare aresold
                                               soldatatthe
                                                        thefixed
                                                             fixedprice
                                                                    priceisisnine
                                                                              nineweeks
                                                                                   weeks
•• Since
       Since products are sold up for nine weeks, the sales period isnine
             products  are sold   up  for nine  weeks,   the  sales period    is nineweeks
                                                                                      weeks
•• IfIfthe   product  did not   sell for nine  weeks,   the product   is discarded
         the product did not sell for nine weeks, the product is discarded
 Parameters and Variables:
Parameters and Variables:
         N: number of products
N: number of products
         T: sales period [weeks]
T: sales period [weeks]
         t: elapsed periods [weeks] (t = 1, …, T)
t: elapsed
         i: productperiods  [weeks]
                         number    (i =(t1,= …,    . . , T)
                                              1, . N)
i: product
         di (t): number
                    shipping(iamount        N)product i in week t
                               = 1, . . . ,of
di (t): Dshipping       amountamount
            i: total delivery     of product        i in week
                                              of product    i t
Di : total      delivery   amount     of  product
         ui (t): shipping rate in week t of product i   i
ui (t): K:     numberrate
          shipping        of clusters
                              in week t of product i
K: number of clusters sales period
         T’:    investigated
          I i ,t : inventory
T’: investigated         salesratio
                                periodof product i in week t
Ii,t : inventory
          X i : random ratio of product i in week t
                             variable representing the realized inventory ratio of product i
Xi : random variable representing the realized inventory ratio of product i
         Yi : random
Yi : random
                           variable representing the predicted inventory ratio of product i
                     variable representing the predicted inventory ratio of product i
          μ ′ : conditional
µ0 : conditional                expectation
                        expectation
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       μX : average of X i
       μY : average
µ X : average  of Xi    Y
                     of i
µY : average of Yi
       ρ: correlation coefficient
ρ: correlation coefficient
       σ x : variance of X i
σx : variance  of Xi
       σ Y : variance
σY : variance  of Yi
                      of i
                          Y
 0
σ : variance in conditional probability
       σ ′ : variance in conditional probability
4.2. Decision-Making Process for Shipping Personnel
 4.2. Decision-Making Process for Shipping Personnel
      Based on the above parameters and variables, Figure 4 shows the decision-making process
      Based on the above parameters and variables, Figure 4 shows the decision-making process of
of shipping personnel. It has seven steps. This paper proposes methods for supporting shipping
 shipping personnel. It has seven steps. This paper proposes methods for supporting shipping
personnel who are in charge of each decision-making process.
 personnel who are in charge of each decision-making process.

                               Figure 4. Decision-Making Process for Shipping Personnel.
                               Figure 4. Decision-Making Process for Shipping Personnel.
     These steps are for product i.
      These steps are for product i.
Step 1. Product i arrives at the logistics warehouse from a plant, and its quantity is Di .
Step 1. Product i arrives at the logistics warehouse from a plant, and its quantity is Di.
Step
Step2.2. Shipping  personnel
            Shipping          practice
                      personnel          firstfirst
                                   practice    shipment
                                                    shipmentof product     i based
                                                                   of product        on a sales
                                                                                 i based     on apolicy   which is
                                                                                                   sales policy     givenis
                                                                                                                  which
         by given
            manufactures   and   its quantity   is
                  by manufactures and its quantity d i (1). is di (1).
Step 3.  Shipping  personnel   recognize    sales  information
Step 3. Shipping personnel recognize sales information              of product
                                                                        of producti fori for
                                                                                          oneone
                                                                                              week.
                                                                                                  week.
Step 4.  Shipping  personnel   consider   and   decide    whether     to ship  additional
Step 4. Shipping personnel consider and decide whether to ship additional product             product   during
                                                                                                          during the next
                                                                                                                   the next
        week.  At this time, they  refer not  only   to  sales quantity    of product     i but also
            week. At this time, they refer not only to sales quantity of product i but also to sales to sales information
         of similar    products
             information          sold last
                             of similar          year and
                                             products    soldcurrent   trends.
                                                                last year   and current trends.
Step
Step5.5. Based
             Basedon on
                      shipping   personnel
                          shipping     personnel  decision,
                                                      decision,product    i is shipped
                                                                    product                whose
                                                                                i is shipped        quantity
                                                                                                whose           is di (t)
                                                                                                          quantity    is dat  t-th
                                                                                                                           i (t) at t-th
         week.
             week.In the  determination
                     In the   determination    of the
                                                    of quantity,
                                                       the quantity,the inventory
                                                                         the inventory of theofstore
                                                                                                 the and
                                                                                                       storethe
                                                                                                             and scale
                                                                                                                   theof    the store
                                                                                                                         scale   of the
         arestore
              takenareintotaken  into consideration.
                            consideration.                     Then, if decide
                                                  Then, if personnel       personnel not decide
                                                                                          to makenot      to make anshipment,
                                                                                                      an additional       additional
             shipment,
         shipping          shipping
                     quantity    of the    productofdithe
                                        quantity          (t) product
                                                              is zero. di (t) is zero.
Step6.6. If the
Step         If the next
                 next      week,
                       week,   t + t1,+ is
                                         1, end
                                            is end   of sales
                                                  of sales      period
                                                            period       T, go
                                                                      T, go       to Step
                                                                              to Step       7. Otherwise,
                                                                                        7. Otherwise,         shipping
                                                                                                           shipping        personnel
                                                                                                                       personnel
             return
         return       to Step
                  to Step      3 and
                            3 and        repeat
                                    repeat     fromfrom
                                                      StepStep
                                                             3 to3 Step
                                                                   to Step   5 until
                                                                         5 until       they
                                                                                    they      fulfill
                                                                                         fulfill  StepStep
                                                                                                         6. 6.
Step7.7. Shipping
Step         Shipping    personnel
                      personnel          finish
                                    finish        their
                                              their     decision.
                                                     decision.
Sustainability 2019, 11, 259                                                                                                     7 of 14

4.3. Product Data Extraction
     Products in the apparel and textile industry come in many categories, colors, and sizes; thus,
      Sustainability
the amount      of 2019, 11 FOR product
                     available   PEER REVIEW
                                           data enormous. Further, customer demand is uncertain, and7sales
area affected by fashion and other industry trends that are in a state of constant flux. In light of these
      4.3. Product Data Extraction
circumstances, the data that shipping personnel have access to at any given time is limited in scope.
Therefore,Products      in the apparel
              when analyzing         ourand
                                          owntextile
                                                data,industry
                                                        we dividecome thein many   categories,
                                                                              products         colors, and
                                                                                         into several      sizes; thus,
                                                                                                        groups,         the data
                                                                                                                   extract
      amount of available product data enormous. Further, customer demand is uncertain, and sales area
from products likely to require shipping plan revision, and analyze them.
      affected by fashion and other industry trends that are in a state of constant flux. In light of these
     An example of the actual change in inventory in a logistics warehouse is shown in Table 1. There is
      circumstances, the data that shipping personnel have access to at any given time is limited in scope.
a significant
      Therefore, difference   in product
                     when analyzing     our quantities
                                            own data, we  even   in the
                                                               divide  the first week, into
                                                                              products  making   it difficult
                                                                                            several  groups, to  see inventory
                                                                                                              extract data
transitions   of all products
      from products      likely toon  one scale
                                   require       of inventory
                                           shipping                quantity.
                                                       plan revision,            Therefore,
                                                                          and analyze   them.the shipping ratio is calculated
as the incoming
            An example inventory     in each
                            of the actual      week
                                          change       di (t), normalized
                                                  in inventory     in a logisticsbywarehouse
                                                                                    the total isarrival  in Table 1.D
                                                                                                 shown quantity       i of each
                                                                                                                     There
      is ai:significant difference in product quantities even in the first week, making it difficult to see
product
      inventory transitions of all products on one scale ofdinventory (t)         quantity. Therefore, the shipping ratio
                                                        ui ( t ) = i .                                                       (1)
      is calculated as the incoming inventory in each weekD           dii(t), normalized by the total arrival quantity Di
       of each product i:
      After calculating the shipping rate for each product, a k-means cluster analysis of ui (t) is conducted
for t = 1, . . . , 9, with a sample of N = 796 uin(order        dito( t divide
                                                                        )
                                                        i t) =            .     products into groups. Since the (1)   number
of pieces of data is as large as N = 796, we decided             Di to use nonhierarchical instead of hierarchical
clustering.After     calculating
               To calculate      thethe shipping
                                     distance      rate forsamples,
                                                between       each product,      a k-means
                                                                          Euclidean         cluster
                                                                                      distance       analysis
                                                                                               is used.  One of   ui(t) is
                                                                                                               disadvantage
of the k-means method is the dependence on the initial value. Therefore, some initial valuesthe
      conducted      for t = 1, …,  9, with a sample   of N = 796  in   order to divide products  into groups. Since    are set
      numberanalysis
and cluster       of piecesis of   data is as and
                                performed,     largeinitial
                                                      as N values
                                                            = 796, we   are decided
                                                                            chosen toto minimize
                                                                                        use nonhierarchical   instead
                                                                                                    the distance  withinof the
      hierarchical clustering. To calculate the distance between samples, Euclidean distance is used. One
average   cluster. The results of the cluster analysis leads to patterns, here called sales policies (i.e.,
      disadvantage of the k-means method is the dependence on the initial value. Therefore, some initial
policies involving selling by advertising products that will be recognized by customers vs. policies to
      values are set and cluster analysis is performed, and initial values are chosen to minimize the distance
sell normally,
      within theasaverage
                       standard     products).
                                cluster.  The results of the cluster analysis leads to patterns, here called sales
       policies (i.e., policies involving selling by advertising products that will be recognized by customers
                                       Table 1. Examples of Changes in Inventory.
       vs. policies to sell normally, as standard products).
                                                      Change in Inventory in Each Week
                                                     Table 1. Examples of Changes in Inventory.
           Product         0                2    1 3       4       5      6                            7       8        9
                                         Change in Inventory in Each Week
             A           2884     291      266   240     198     154    123                            80      44       36
        Product         0       1        2       3        4        5       6                             7        8        9
             B           2078     1151    1038   347     221     171    122                            0        0       0
           AC         2884293  291 249  266248  240
                                                 220     198
                                                         220      154
                                                                 220      123
                                                                        191                           11680    94 44    32 36
           B          2078    1151     1038     347      221      171     122                              0        0        0
           C           293     249      248     220      220      220     191                           116       94       32
     The result of the k-means method suggested that it was reasonable to divide the analyzed data
into two groups,   which
           The result of thewere
                            k-meansthen   roughly
                                        method      dividedthat
                                                 suggested    into  five reasonable
                                                                 it was    groups to toprovide
                                                                                          divide more   detail. data
                                                                                                 the analyzed    Figure 5
shows into
        thetwo groups,
            average     which
                      value  ofwere   then roughly
                                inventory     ratios divided
                                                     in each into
                                                              week fiveforgroups  to the
                                                                            each of  provide
                                                                                          five more  detail.
                                                                                               clusters.     Figure 5 on
                                                                                                         Depending
      shows thepercentages
the shipment     average valueinofthe
                                    inventory  ratios
                                       first week,    in each
                                                    five      weekcan
                                                         clusters     forbeeach of the five
                                                                             broadly        clusters. Depending on
                                                                                        categorized.
       the shipment percentages in the first week, five clusters can be broadly categorized.
                              1
                            0.9
                            0.8
                            0.7
                               Inventory Ratio

                            0.6
                            0.5
                            0.4
                            0.3
                            0.2
                            0.1
                              0
                                 0      1     2      3     4      5    6     7     8     9
                                                                             Week

                                                                  1      2       3      4         5
                           Figure 5. Average
                              Figure 5. AverageInventory
                                                 InventoryRatios in Each
                                                          Ratios in EachWeek
                                                                         Weekfor
                                                                               forEach
                                                                                   Each  Cluster.
                                                                                       Cluster.
Sustainability 2019, 11, 259                                                                          8 of 14

     For clusters 1 and 2, the shipment ratio in the first week is high. On the other hand, in clusters 3,
4, and 5, the shipment ratio of the first week is low. Investigating the characteristics of each cluster
further, products of clusters 1 and 2 represent the policy that a manufacturer wants to sell featured
products. Also, the trend of shipment ratios from the second to the ninth week shows that products
remaining in the logistics warehouse are gradually shipped until the end of the sale period. Therefore,
the shipping personnel will not revise the shipping plan later. On the contrary, products in clusters 3,
4, and 5 demonstrate a policy whereby the shipping personnel sell the product in stages, conditional
on the level of sales. Accordingly, products belonging to these classes are highly likely to have been
subject to revised shipping plans. In other words, shipping personnel should have recognized products
exhibiting this kind of sales information.

4.4. Forecasting Inventory Ratios
     The cluster analysis identifies products that shipping personnel should recognize as undergoing
significant changes in inventory. However, the shipping personnel do not know the optimal time or
other factors about the shipment. Therefore, the reference lines obtained by cluster analysis (Figure 5)
predict the inventory ratio at certain weeks. Changes in inventory that deviate significantly from
the basic line are signals that should be transmitted to shipping personnel to highlight important
sales information.
     In this paper, to predict how far the inventory transition will be from the basic line, the conditional
probability of the bivariate normal distribution is used for each product. In this way, it is possible to
predict the subsequent inventory transition when the change in inventory is recognized until a specific
week. The conditional expectation and variance in the conditional probability of the bivariate normal
distribution are obtained by the following Equations (2) and (3), respectively.

                                                            Ii,t − µ X
                                         µ0 = µY + ρσY                 ,                                 (2)
                                                                 σx
                                                   q
                                         σ0 = σY       1 − ρ2 (≤ σY ).                                   (3)

     Based on the above conditional expectation and the conditional variance of the conditional
probability, a 95% confidence interval is generated, which is used as the range of prediction. However,
since the actual inventory ratio may be smaller than the inventory ratio considering 95% confidence
intervals for the conditional expectation obtained by the conditional probability of the bivariate normal
distribution, this paper proposes minimum values for each week. Since the inventory ratio cannot be
smaller than zero, it is considered to be the minimum. Hence, the upper and lower limits of the range
from the inventory ratio considering the 95% confidence interval and the actual inventory ratio are
as follows:
                                  Upper limit : Min µ0 + 1.96σ0 , Ii,t ,
                                                     
                                                                                                       (4)

                                   Lower limit : Max µ − 1.96σ0 , 0 .
                                                       0
                                                                                                       (5)

     Here, we predict the inventory ratio of product A using information on all clusters of products to
be sold in stages, namely, clusters 3, 4, and 5, and for the cluster to which it belongs, 3. The prediction
for product A is shown below. The gray line of each figure is a line connecting the conditional
expectation values at each week calculated by the Equation (2). The blue line represents change of the
upper limit value in each week obtained from Equation (4). The orange line shows change of the lower
limit derived from Equation (5). Finally, in order to compare how the actual inventory ratio changes to
changes of gray, blue, orange lines, the change of the actual inventory ratio is indicated by yellow line.
Here, the calculation results are shown assuming that the sales period is T = 9. Therefore, based on the
assumption, the products will not be sold after nine weeks and will be discarded.
Sustainability 2019, 11, 259                                                                                                                    9 of 14
Sustainability 2019, 11 FOR PEER REVIEW                                                                                                               9

     The shipment
     The  shipment of of the
                          the first
                               first week
                                     week isis determined
                                                determined by by the
                                                                  the manufacturer’s
                                                                       manufacturer’s sales sales policy,
                                                                                                  policy, and
                                                                                                            and shippers
                                                                                                                  shippers
who   oversee  shipping    decisions   begin   shipping   after the  second    week.   Therefore,
who oversee shipping decisions begin shipping after the second week. Therefore, this paper predicts  this  paper   predicts
inventory levels
inventory   levels for
                    forall
                         allweeks,
                             weeks,conditional
                                       conditional   onon
                                                        thethe
                                                            realized   level
                                                                realized       of sales
                                                                            level       up toup
                                                                                   of sales     anytogiven    week. week.
                                                                                                       any given     Form
Figure  6a,b, since the  shipping    ratio at  the  third week   is large,  the  range  of  prediction
Form Figure 6a,b, since the shipping ratio at the third week is large, the range of prediction after the  after the fourth
week can
fourth weekbecan narrowed
                   be narrowedsignificantly.
                                    significantly.Furthermore,
                                                      Furthermore,with   thethe
                                                                      with      expected
                                                                                  expectedvalue
                                                                                              valueof of the  conditional
                                                                                                          the conditional
probability, which
probability,  which isis the
                          the gray
                              gray line,
                                     line, at
                                            at the
                                                the time
                                                     time when
                                                          when thethe inventory
                                                                       inventory ratio
                                                                                     ratio up
                                                                                            up to
                                                                                                to the
                                                                                                    the second
                                                                                                         second week
                                                                                                                   week isis
known,   the  inventory    ratio  of the ninth     week  has  already   come     close to  the  actual
known, the inventory ratio of the ninth week has already come close to the actual inventory ratio.       inventory    ratio.
Therefore,in
Therefore,  inthe
               thecase
                   caseofofproduct
                             productA, A,the
                                           theinventory
                                                 inventoryratio
                                                            ratiothat
                                                                   thatwill
                                                                        will   result
                                                                            result  inin disposal
                                                                                       disposal      could
                                                                                                  could    bebe  predicted
                                                                                                              predicted   at
at the
the    second
    second  week.week.   Shipping
                    Shipping          personnel
                                personnel           who know
                                             who know             this
                                                           this can     canreduce
                                                                     then     then reduce     the amount
                                                                                     the amount     of product of disposal
                                                                                                                   product
disposal
by        by considering
   considering               various countermeasures
                 various countermeasures           and takingand  taking action.
                                                               action.

                          1                                                                                  1

                        0.8                                                                                 0.8

                                                                                          Inventory Ratio
      Inventory Ratio

                        0.6                                                                                 0.6

                        0.4                                                                                 0.4

                        0.2                                                                                 0.2

                          0                                                                                  0
                              0       2          4          6           8                                         0   2    4       6        8
                                                Week                                                                        Week
                                              (a)                                                                         (b)
                         1                                                                                  1

                        0.8                                                                            0.8
                                                                                     Inventory Ratio
   Inventory Ratio

                        0.6                                                                            0.6

                        0.4                                                                            0.4

                        0.2                                                                            0.2

                         0                                                                                  0
                              0      2           4          6          8                                          0   2    4       6        8
                                                 Week                                                                      Week
                                              (c)                                                                         (d)
                     Figure  6. The
                     Figure 6.  The Expectation
                                      Expectation for Product
                                                         Product A A (conditional
                                                                      (conditional on data of clusters
                                                                                                    clusters 3, 4,4, and
                                                                                                                     and 5).
                                                                                                                          5). Note:
                                                                                                                               Note: graph (a)
                     represents
                     representswhen
                                 whenthe  theactual
                                              actualinventory
                                                       inventoryratio
                                                                  ratiois is
                                                                           known
                                                                             known  byby
                                                                                       thethe
                                                                                            second
                                                                                               secondweek,  (b)(b)
                                                                                                        week,    is when   it isitknown
                                                                                                                     is when       is knownby the
                                                                                                                                               by
                     third week,  (c)  is when  it is  known  by  the  fourth    week,  and   (d) is when   it is known
                     the third week, (c) is when it is known by the fourth week, and (d) is when it is known by the fifth   by  the  fifth week.
                     The gray
                     week.  Theline
                                 grayshows   the conditional
                                        line shows             expectation,
                                                      the conditional            the blue
                                                                        expectation,    theand  orange
                                                                                             blue        lines show
                                                                                                   and orange     linesthe
                                                                                                                        showupper     and lower
                                                                                                                                the upper    and
                     limits
                     lower of  the range,
                            limits  of the respectively,   and theand
                                            range, respectively,    yellow the line shows
                                                                               yellow   linethe  change
                                                                                              shows   the in the actual
                                                                                                           change    in theinventory     ratio of
                                                                                                                             actual inventory
                     product  A.
                     ratio of product    A.

     In both Figures 6 and 7, the more weeks in which the inventory ratio is known, the narrower the
     In both Figures 6 and 7, the more weeks in which the inventory ratio is known, the narrower
range of prediction. In the case of product A, the prediction range is narrowed significantly in the
the range of prediction. In the case of product A, the prediction range is narrowed significantly
third week. This is because the actual inventory ratio of product A is drastically reduced in the third
in the third week. This is because the actual inventory ratio of product A is drastically reduced
week.   Moreover,
in the third   week.when     predicting
                      Moreover,    whenwith     only the
                                           predicting     cluster
                                                       with         to which
                                                              only the   clusterproduct
                                                                                   to which A product
                                                                                               belongs,Athe  prediction
                                                                                                           belongs,
range
the prediction range is narrowed as a whole. However, product A is shipped at a high rate inThen,
       is narrowed     as a  whole.  However,    product   A   is shipped    at a  high rate  in the third  week.
the
the inventory
    third week.  ratio  at the
                    Then,   thethird  week ratio
                                inventory    is much   smaller
                                                   at the third than
                                                                   weekthe   expected
                                                                          is much         inventory
                                                                                      smaller         ratio
                                                                                                than the    of the third
                                                                                                          expected
week  at the
inventory      second
             ratio      week.
                   of the  third The
                                 weekactual
                                        at thesales areweek.
                                               second   not known       at that
                                                                The actual        time,
                                                                              sales  are but
                                                                                         not shipping
                                                                                              known at more     than the
                                                                                                         that time,
expected
but shipping more than the expected value may result in more waste. Hence, excess shipping the
            value  may    result in more    waste.  Hence,    excess  shipping      can  be  reduced   by  shipping
product   in the fourth
can be reduced            week after
                   by shipping     the receiving
                                        product in more
                                                     the detailed
                                                         fourth weeksalesafter
                                                                            information.
                                                                                 receivingInmoreotherdetailed
                                                                                                      words, sales
                                                                                                               since this
product   is highly
information.        likelywords,
                In other    to result in some
                                    since  this disposal,
                                                product isit is possible
                                                             highly        to reduce
                                                                      likely           extra
                                                                               to result      shipping
                                                                                           in some      by lengthening
                                                                                                     disposal,  it is
possible to reduce extra shipping by lengthening the period for recognizing sales information.
Sustainability 2019, 11, 259                                                                                                                   10 of 14
Sustainability 2019, 11 FOR PEER REVIEW                                                                                                              10

As
the in the other
     period        method, when
             for recognizing    salesshipping  at theAs
                                      information.    third  week,
                                                         in the     it method,
                                                                other  is better when
                                                                                 to adjust the shipping
                                                                                       shipping   at the third
amount
week, it of product
         is better to A. For the
                      adjust   example,  product
                                   shipping       A isofshipped
                                             amount      productatA.proportions
                                                                      For example,according
                                                                                     producttoAthe  basic at
                                                                                                is shipped
line (gray line
proportions     of Figureto6 the
              according       or Figure 7). (gray line of Figure 6 or Figure 7).
                                 basic line

                         1                                                                                 1

                    0.8                                                                                   0.8

                                                                                      Inventory Ratio
  Inventory Ratio

                    0.6                                                                                   0.6

                    0.4                                                                                   0.4

                    0.2                                                                                   0.2

                         0                                                                                 0
                              0        2          4           6          8                                      0   2     4      6         8
                                                  Week                                                                    Week
                                                (a)                                                                     (b)
                          1                                                                                1

                        0.8                                                                               0.8
                                                                                        Inventory Ratio
      Inventory Ratio

                        0.6                                                                               0.6

                        0.4                                                                               0.4

                        0.2                                                                               0.2

                          0                                                                                0
                              0         2          4          6          8                                      0   2    4       6        8

                                                   Week                                                                  Week
                                                 (c)                                                                    (d)

                                   TheConditional
                        Figure 7. The  ConditionalProbability
                                                       ProbabilityExpectation
                                                                      Expectationofofthe  theBivariate
                                                                                               Bivariate   Normal
                                                                                                         Normal     Distribution
                                                                                                                  Distribution   of of Product
                                                                                                                                    Product  A
                        A  for Data of Cluster   3. Note:   graph   (a) represents    when    the  actual  inventory
                        for Data of Cluster 3. Note: graph (a) represents when the actual inventory ratio is known by ratio  is known   by  the
                        second week,
                        second  week, (b)
                                       (b) is
                                           is when
                                               when itit is
                                                         is known
                                                            known by by the
                                                                         the third
                                                                              third week,
                                                                                    week, (c)(c) is
                                                                                                 is when
                                                                                                    when itit is
                                                                                                              is known
                                                                                                                 known byby the
                                                                                                                            the fourth
                                                                                                                                 fourth week,
                                                                                                                                          week,
                                   when it is
                        and (d) is when     is known
                                               known by by the
                                                            the 5th
                                                                5th week.
                                                                     week. The
                                                                             The gray
                                                                                  gray line
                                                                                         line shows
                                                                                              shows thethe conditional
                                                                                                           conditional expectation,
                                                                                                                        expectation, the blue
                        and orange lines show the the upper
                                                      upper and
                                                              and lower
                                                                    lower limits
                                                                           limits of
                                                                                   of the
                                                                                       therange,
                                                                                           range,respectively,
                                                                                                    respectively, and the yellow line shows
                                                                                                                                         shows
                        the change in the actual inventory ratio of product A.

      As aa second
      As    second example,
                      example, thethe prediction
                                      prediction results
                                                    results for
                                                              for product
                                                                   product B   B are
                                                                                   are shown
                                                                                        shown in in Figures
                                                                                                    Figures 88 and
                                                                                                                and 9.
                                                                                                                     9. Product
                                                                                                                         Product
B  is also sold  in  stages,  and   the  detailed   cluster    number      is  5.  As   with   product
B is also sold in stages, and the detailed cluster number is 5. As with product A, we predict cases      A, we    predict   cases
                                                                                                                               for
which the actual inventory ratio is known in the second week. The figures show that product B has B
for  which   the actual   inventory    ratio is  known    in   the   second     week.     The  figures  show    that  product    a
has ainventory
high   high inventory      ratioateven
                   ratio even           at theweek.
                                   the ninth   ninth Also,
                                                       week.inAlso,      in the
                                                                   the case    of case
                                                                                   productof product   B, the predicted
                                                                                              B, the predicted              ninth
                                                                                                                  ninth week’s
week’s inventory
inventory    ratio atratio
                        the at  the second
                             second    weekweek
                                              does does     not differ
                                                      not differ      much muchfrom  fromthethe  prediction
                                                                                              prediction   atatthe
                                                                                                                 thefifth
                                                                                                                     fifthweek.
                                                                                                                           week.
Therefore,    some   degree    of  prediction   is possible     in  the  second       week.    Furthermore,
Therefore, some degree of prediction is possible in the second week. Furthermore, as can be seen                as can   be  seen
                                                                                                                                in
in  Figure  9d, the  inventory     ratio at the  sixth  week     is lower     than    the  expected
Figure 9d, the inventory ratio at the sixth week is lower than the expected value, suggesting that    value,  suggesting      that
shipments were
shipments     were made
                    made to to avoid
                               avoid being
                                       being left
                                              left with
                                                    with aa large
                                                             large inventory
                                                                     inventory in   in the
                                                                                        thelogistics
                                                                                             logisticswarehouse.
                                                                                                       warehouse.However,
                                                                                                                       However,
since  the  product    is unlikely   to sell much     after  being    shipped       in  the
since the product is unlikely to sell much after being shipped in the sixth week, perhaps it sixth  week,  perhaps     it should
                                                                                                                          should
have   been  shipped    earlier  to increase  sales.  By  shipping      in  this   manner,    the  product
have been shipped earlier to increase sales. By shipping in this manner, the product would have been        would     have   been
placed in
placed   in the
            the store
                 store for
                        for aa longer
                               longer period,     and opportunities
                                        period, and    opportunities to      to sell
                                                                                sell atat the
                                                                                           the fixed
                                                                                               fixed price
                                                                                                      price would
                                                                                                            would alsoalso have
                                                                                                                            have
increased.   This  would    have   reduced   the   amount     of  waste    due
increased. This would have reduced the amount of waste due to unsold product.     to  unsold    product.
     When using the results of prediction, first, the shipping personnel would compare the
conditional expectation with the inventory ratio of the product at the present moment. This shows
how the inventory ratio of the product changes with respect to the average. Then, the shipping
personnel would plan the shipping for the next week. Finally, they would determine the amounts of
the shipment while also taking into account the sales policy.
Sustainability 2019, 11, 259                                                                                                                 11 of 14
             Sustainability 2019, 11 FOR PEER REVIEW                                                                                    11

                                      1                                                            1

                                    0.8                                                          0.8

                                                                               Inventory Ratio
                  Inventory Ratio
                                    0.6                                                          0.6

                                    0.4                                                          0.4

                                    0.2                                                          0.2

                                      0                                                            0
                                          0   2         4      6   8                                       0   2     4          6   8
                                                    Week                                                                 Week
                                                  (a)                                                              (b)
                                      1                                                           1

                                    0.8                                                          0.8

                                                                            Inventory Ratio
                Inventory Ratio

                                    0.6                                                          0.6

                                    0.4                                                          0.4

                                    0.2                                                          0.2

                                      0                                                           0
                                          0   2     4          6   8                                   0       2     4          6   8
                                                        Week                                                             Week
                                                  (c)                                                              (d)

      Figure 8. TheFigure    8. The Expectation
                          Expectation              of Product
                                              of Product      B (conditional on
                                                           B (conditional     ondata
                                                                                   dataforfor
                                                                                           clusters 3, 4, and
                                                                                               clusters        5).and
                                                                                                           3, 4,   Note:5).
                                                                                                                         graph (a) graph (a)
                                                                                                                            Note:
                   represents when the actual inventory ratio is known by the second week, (b) is when it is known by
      represents when the actual inventory ratio is known by the second week, (b) is when it is known by the
                   the third week, (c) is when it is known by the fourth week, and (d) is when it is known by the fifth
      third week,     (c) is
                   week.    Thewhen     it isshows
                                 gray line     known    by the fourth
                                                   the conditional       week,the
                                                                   expectation,   and
                                                                                    blue(d)
                                                                                          andisorange
                                                                                                whenlinesit isshow
                                                                                                                known     by the
                                                                                                                    the upper andfifth week.
      The gray linelower shows     the
                            limits of theconditional     expectation,
                                           range, respectively,          the blue
                                                                and the yellow  line and
                                                                                     shows orange    lines
                                                                                             the change   in show    theinventory
                                                                                                             the actual   upper and lower
      limits of theratio  of product
                       range,          B.
                                  respectively,     and the yellow line shows the change in the actual inventory ratio of
            Sustainability 2019, 11 FOR PEER REVIEW                                                                                 12
      product   B.
                  Also, the results of this prediction lead to different recommendations depending on the type of
             product.
                    1  For example, in the case of a standard product,   1 manufacturers sell for a longer term, so if
             the inventory runs out earlier than forecasted, it is possible to produce additional products to meet
                  0.8                                                  0.8
             customer   demand. On the other hand, in the case of a product sold for only one season, when the
                                                                          Inventory Ratio
               Inventory Ratio

             expected
                  0.6
                       value of the stock ratio at the ninth week is large,
                                                                       0.6 this is a signal that products are not selling
             well that should be heeded by shipping personnel.
                  0.4                                                  0.4
                  In QR strategy in the logistics warehouse, product       shipping quantities are decided at the time
             when0.2shipping personnel receive sales information on    0.2each product during the monitoring period.
             However, in this paper, we give a signal to shipping personnel that is based on the comparison of
             previous
                    0  inventory transition for a similar product to the 0 current inventory transition for the current
                                                                            0        2         4       6         8
             product.0 Therefore,
                              2
                                  even 4if there is
                                                  6        8
                                                     no arrival of sales information,   shipping  personnel  can receive
                                          Week                                                 Week
             signals about shipping. In addition, this method is effective for all sales periods.
                                      (a)                                                    (b)
                                     1                                                            1

                                    0.8                                                       0.8
                                                                           Inventory Ratio
                Inventory Ratio

                                    0.6                                                       0.6

                                    0.4                                                       0.4

                                    0.2                                                       0.2

                                     0                                                            0
                                          0   2     4          6   8                                   0       2    4           6   8
                                                        Week                                                         Week
                                                  (c)                                                              (d)

      Figure 9. Figure  9. The Conditional
                  The Conditional             ProbabilityExpectation
                                         Probability       Expectation of of
                                                                          thethe
                                                                              Bivariate  NormalNormal
                                                                                   Bivariate      Distribution of Product Aof Product
                                                                                                           Distribution
                 for Data of Cluster 5. Note: graph (a) represents when the actual inventory ratio is known by the
      A for Data of Cluster 5. Note: graph (a) represents when the actual inventory ratio is known by the
                 second week, (b) is when it is known by the third week, (c) is when it is known by the fourth week,
      second week,     (b)
                 and (d) is is when
                            when  it is it is known
                                        known   by the by
                                                        fifththe third
                                                              week. The week,
                                                                        gray line(c)shows
                                                                                      is when    it is known
                                                                                           the conditional       by the the
                                                                                                            expectation,  fourth week,
      and (d) is blue
                  whenanditorange
                            is known     by the
                                  lines show   thefifth week.
                                                    upper        Thelimits
                                                           and lower  grayofline
                                                                               the shows    the conditional
                                                                                   range, respectively,  and theexpectation,
                                                                                                                 yellow line   the blue
      and orange shows  theshow
                    lines   change  in the
                                  the       actual
                                        upper   andinventory
                                                      lowerratio   of product
                                                               limits          A.
                                                                      of the range,     respectively, and the yellow line shows
      the change in the actual inventory ratio of product A.
             5. Conclusions
                  In this study, based on the premise of selling at fixed price, we tested an approach for reducing
             waste from unsold products in the textile and apparel industry and, thereby, mitigating adverse
             effects on the environment. The purpose of shipping personnel in the study is to recognize relevant
             data about sales situations and make appropriate judgments (i.e., predictions) about whether to issue
             alerts. The alerts in this paper are made from the result of data analysis to the product that shipping
             personnel should watch sales situation carefully. Although there are many kinds of data that can be
Sustainability 2019, 11, 259                                                                         12 of 14

     When using the results of prediction, first, the shipping personnel would compare the conditional
expectation with the inventory ratio of the product at the present moment. This shows how the
inventory ratio of the product changes with respect to the average. Then, the shipping personnel
would plan the shipping for the next week. Finally, they would determine the amounts of the shipment
while also taking into account the sales policy.
     Also, the results of this prediction lead to different recommendations depending on the type of
product. For example, in the case of a standard product, manufacturers sell for a longer term, so if
the inventory runs out earlier than forecasted, it is possible to produce additional products to meet
customer demand. On the other hand, in the case of a product sold for only one season, when the
expected value of the stock ratio at the ninth week is large, this is a signal that products are not selling
well that should be heeded by shipping personnel.
     In QR strategy in the logistics warehouse, product shipping quantities are decided at the time
when shipping personnel receive sales information on each product during the monitoring period.
However, in this paper, we give a signal to shipping personnel that is based on the comparison of
previous inventory transition for a similar product to the current inventory transition for the current
product. Therefore, even if there is no arrival of sales information, shipping personnel can receive
signals about shipping. In addition, this method is effective for all sales periods.

5. Conclusions
      In this study, based on the premise of selling at fixed price, we tested an approach for reducing
waste from unsold products in the textile and apparel industry and, thereby, mitigating adverse effects
on the environment. The purpose of shipping personnel in the study is to recognize relevant data
about sales situations and make appropriate judgments (i.e., predictions) about whether to issue
alerts. The alerts in this paper are made from the result of data analysis to the product that shipping
personnel should watch sales situation carefully. Although there are many kinds of data that can
be analyzed in this particular industry, we chose to focus on logistics warehouse data, examining
stock points to assess changes in the warehouse inventory ratios. Since the total quantities of apparel
products varied considerably, the data was normalized in our study. Furthermore, because it was
difficult to monitor the status of each individual product, we categorized products into several groups
using cluster analysis. We found that the products whose sales information required the most careful
monitoring were products that were sold in stages. For these products, we also forecasted inventory
ratios using cluster results, and predictions showed that some products were more likely to remain
unsold. Given this, we considered the products whose shipment patterns (i.e., timing and quantities)
should be modified.
      This study has practical value for shipping personnel. By using conditional probability in the
manner we have proposed, shipping personnel could accurately predict inventory ratios at the ninth
week from changes in the inventory ratios up to the third week. Therefore, at the third week, shipping
personnel could take remedial measures for products predicted to have excess inventory in the
logistics warehouse.
      In light of the trade-off between the risk of disposal from unsold product and the risk of
opportunity loss from product shortage, future research should investigate optimal shipment timing
when disposal and shortage are simultaneously taken into consideration. Also, the optimal shipping
quantities should be obtained at the optimum shipment timing. In practice, however, the timing or
quantities of products shortage cannot be obtained as data. Therefore, under the assumption of a
product shortage situation, the risk of opportunity loss will be evaluated. In addition, future research
should verify the effectiveness of the proposed method by performing analyses in several different
scenarios. In sum, using past data as well as current sales data can allow for better detection of
market trends. Although the larger the amount of data, the easier it is to detect market trends in
past and present, to do so, many textile and apparel companies are needed to share and analyze data.
Apparel and textile companies can use our findings to improve the timing and quantity of shipments,
Sustainability 2019, 11, 259                                                                                13 of 14

more effectively manage supply chains, and protect profits. In so doing, they can also reduce the
burden of disposal, minimize adverse effects on the environment, and contribute to the development
of more sustainable societies.

Author Contributions: R.T. performed the research and wrote the manuscript. A.I. coordinated and supervised
the overall research. T.S. assisted in developing mathematical methods. M.H. and W.K. acquired funds and
collected data. All authors read and approved the final manuscript.
Conflicts of Interest: The authors declare no conflict of interest.

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