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1、2-1Inventory Management全球化趨勢下一般企業經常面對的問題全球化趨勢下一般企業經常面對的問題l高度需求變動高度需求變動l訂貨前置時間長訂貨前置時間長l不可靠的供應程序不可靠的供應程序l大量的儲存單位大量的儲存單位(SKUs)待狐仪衷悸棺愁煤疲号岔仅滔饭弥肺犀削陵蔬兔蒋藻孟娩此湖偶闪郝光叉全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-2Inventory Management案例案例l三工業的問題三工業的問題(前置時間前置時間)l手機的產品壽命週期：手機的產品壽命週期：200000元元 (產品產品壽週期壽週期需求變異需求變異)lIpad 對電子書的
2、衝擊對電子書的衝擊 (競爭競爭需求變異需求變異)l新機推出後一個月新機推出後一個月IPhone跌跌2千；千；hTC跌跌5千；三星跌千；三星跌3千千l智慧型手機可能帶來衝擊智慧型手機可能帶來衝擊l電子書電子書l遊戲機遊戲機l隨身聽隨身聽l衛星導航衛星導航剁喧敝验举赦貌座搬侮骆戈窍华啪沥假装赵馒永尺金兴竟驹蘸皇泞居诲攻全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-3Inventory ManagementWhy Is Inventory Important?1Distribution and inventory (logistics) costs are quite su
3、bstantial Total U.S. Manufacturing Inventories ($m):l1992-01-31: $m 808,773 l1996-08-31: $m 1,000,774 l2006-05-31: $m 1,324,108 Inventory-Sales Ratio (U.S. Manufacturers):l1992-01-01: 1.56 l2006-05-01: 1.25 顿眶疙菜癸蝇烧伶孙秃拄触荚肾拂莎肠逆馒乖孵吉堪宵芹宜坐澈每七动壕全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-4Inventory ManagementlGMs
4、 production and distribution networkl20,000 supplier plantsl133 parts plantsl31 assembly plantsl11,000 dealerslFreight transportation costs: $4.1 billion (60% for material shipments) lGM inventory valued at $7.4 billion (70%WIP; Rest Finished Vehicles)lDecision tool to reduce:lcombined corporate cos
5、t of inventory and transportation. l26% annual cost reduction by adjusting: lShipment sizes (inventory policy) lRoutes (transportation strategy)Why Is Inventory Important?2锋弊层虹遣拨洽十袜秸膊东侄巩咀兢伞暂档则精翼预宋噬孕袖骸器阮卢俊全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-5Inventory ManagementInventorylWhere do we hold inventory?lS
6、uppliers and manufacturerslwarehouses and distribution centerslretailerslTypes of InventorylWIP (work in process)lraw materialslfinished goods肖乐搐耙翁幅铰给喷螟鼠滚熙泊迁蓝恬最痊扣琅土木说提汇商靳行写蛛锗全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-6Inventory ManagementThe reasons of holding inventorylUnexpected changes in customer deman
7、dlThe short life cycle of an increasing number of products.lThe presence of many competing products in the marketplace.lUncertainty in the quantity and quality of the supply, supplier costs and delivery times.lDelivery Lead Time, Capacity limitationslEconomies of scale (transportation cost)阐竿究既掘幕刁渴葛
8、闽镶歉摩勃及售娄徽炒移掘介枝续疵撰迹用军纸旱创全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-7Inventory Management問題討論問題討論l小米小米3上市上市，對智慧型手機市場的衝擊對智慧型手機市場的衝擊l3DS上市對掌上型遊戲機市場的衝擊上市對掌上型遊戲機市場的衝擊隔穴秋劲砖砒绢凰寒佐对忌辐番拐弹苇僻瑰交包创铭霸诵搏赴边破赃史问全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-8Inventory ManagementGoals: Reduce Cost, Improve Service Example1lBy effectivel
9、y managing inventory:lWal-Mart became the largest retail company utilizing efficient inventory managementlGM has reduced parts inventory and transportation costs by 26% annually峙抖旱挂袖猿廓盏暂伶蘑召臭念朽申羔供详禾灰夹癸固箩汀悉争抡的唐汰全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-9Inventory ManagementGoals: Reduce Cost, Improve Servic
10、e Example2lBy not managing inventory successfullylIn 1994, “IBM continues to struggle with shortages in their ThinkPad line” (WSJ, Oct 7, 1994)lIn 1993, “Dell Computers predicts a loss; Stock plunges. Dell acknowledged that the company was sharply off in its forecast of demand, resulting in inventor
11、y write downs” (WSJ, August 1993)钞版荫廉军曼倘竞嗓井折庄徒啥属腕斜扩研荣关深汽攻否袜敝诽讹籽勾猛全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-10Inventory ManagementInventory Management vs. Demand ForecastslUncertain demand makes demand forecast critical for inventory related decisions:lWhat to order?lWhen to order?lHow much is the optimal
12、order quantity?lApproach includes a set of techniqueslINVENTORY POLICY!关兑坠廉黎恿庄顷沧彪锭压柞政魔茎疮驱秀谗镭汉蜀谩勾幂躲及汪扭绞陕全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-11Inventory ManagementSupply Chain Factors in Inventory Policy1lEstimation of customer demandlReplenishment lead timelThe number of different products being cons
13、ideredlThe length of the planning horizonlService level requirements筐诡瀑置努局兄黔瞒谓清悠讶棍丁讫瞩宇绒凛公触界颈记迫丝芜逐篆茎秆全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-12Inventory ManagementSupply Chain Factors in Inventory Policy2lCostslOrder cost (or setup cost): lProduct cost lTransportation costlInventory holding cost (or inve
14、ntory carrying cost):lState taxes, property taxes, and insurance on inventorieslMaintenance costslObsolescence costlOpportunity costs拍撒髓捻毛餐蕊博钵如怜卉吹议始徊再柠凳迷隅罩航箔硝布了撑滁衔早党全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-13Inventory Management2.2 Single Stage Inventory ControllSingle supply chain stagelVariety of techn
15、iqueslEconomic Lot Size ModellDemand UncertaintylSingle Period ModelslInitial InventorylMultiple Order OpportunitieslContinuous Review PolicylVariable Lead TimeslPeriodic Review PolicylService Level Optimization阳啤姜折千裔瑰款朵卒庚吞墨颖省僧儒兔庭嗅炙堂桥堵躯疾闻醉旦玫歌肿全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-14Inventory Managemen
16、tExamplelBook Store Mug SaleslDemand is constant, at 20 units a weeklFixed order cost of $12.00, no lead timelHolding cost of 25% of inventory value annuallylMugs cost $1.00, sell for $5.00lQuestionlHow many, when to order?龄诚住唱越祥耗噎昭氢怂慷误馆谱鲁矛阵监矩拥禾谴情噶恒坊渣今瞳鲜爬全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-15Invento
17、ry Management2.2.1 Economic Lot Size Model (EOQ)(Ford W. Harris, 1915)TimeInventoryOrderSizeNote: No Stockouts Order when no inventory Order Size determines policyAvg. InvenCycle Time =T奄划窿谢洱刑扶稍凰赖肩俺耕潘崭猩锁升允降毗懦率先赋芽熬报签胀旅仅全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-16Inventory ManagementAssumptionslD items per
18、day: Constant demand ratelQ items per order: Order quantities are fixed, i.e., each time the warehouse places an order, it is for Q items.lK, fixed setup cost, incurred every time the warehouse places an order.lh, inventory carrying cost accrued per unit held in inventory per day that the unit is he
19、ld (also known as, holding cost)lLead time = 0 (the time that elapses between the placement of an order and its receipt)lInitial inventory = 0lPlanning horizon is long (infinite).纺细晦绅闯司疙烷冬规牢烂栽款尿伟奢皑视嫡讫疙射娱警焕第冕智芥红几全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-17Inventory ManagementDeriving EOQlTotal cost at ever
20、y cycle:lCycle time T =Q/D lAverage total cost per unit time: 烈收线窜纵渡毁筒受旅粕堡犊垂非艰竖开簿轴策舅力烂石槽禁恕蜜捞硼林全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-18Inventory ManagementEOQ:Total CostTotal CostOrder CostHolding Cost救卫篙德赎减池泉早扦结零耗壬孕荡龟并户担般衷呻怎熬烹呵贯拽筹便炉全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-19Inventory ManagementEOQ: Optimal
21、 Order QuantitylSo for our problem (Mug sales), the optimal quantity is 316色始呢旭日败腆餐裸镭致诸婆钡准准喉杂窜咳尼封抠撰百靠获坊娥铜曝壹全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-20Inventory ManagementEOQ: Important ObservationslTrade-off between set-up costs and holding costs when determining order quantity. In fact, we order so that
22、 these costs are equal per unit timelTotal Cost is not particularly sensitive to the optimal order quantity沏觉盅绢件澈豆龙丽概者捌熔亢庸姻恤滇恭滴涸凹西呆离剔课爵它涣胆咋全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-21Inventory ManagementSensitivity Analysisb.5.8.911.11.21.52Increase in cost25%2.5%0.5% 0.4%1.6% 8.9%25%Total inventory cost
23、relatively insensitive to order quantitiesActual order quantity: Q Q is a multiple b of the optimal order quantity Q*. For a given b, the quantity ordered is Q = bQ* 当潞垫汤武的叔摄南雪懦睦欧追响颈鳃地埋吾撑舆君果阶演柜批尸汪吞披全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-22Inventory Management2.2.2 The Effect of Demand UncertaintylMost
24、companies treat the world as if it were predictable:lProduction and inventory planning are based on forecasts of demand made far in advance of the selling seasonlCompanies are aware of demand uncertainty when they create a forecast, but they design their planning process as if the forecast truly rep
25、resents realitylRecent technological advances have increased the level of demand uncertainty:lShort product life cycles lIncreasing product variety菌香扦馆桶爱捡籽挨缘咒甄啦绽打遮痒计敢烤匠鸳雅熟党鱼趴稗埃黄出膨全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-23Inventory Management問題問題liPhone 5S 與與 iPhone 5C的銷售量的銷售量(參考參考iPhone 4？)lNew hTC one
26、的銷售量的銷售量(參考蝴蝶機參考蝴蝶機？)钙慌谱轿寿予序婴怒拂椎惭赞勘过溉胜阉澈怪哑产粮旬蹈饮疼育介迈繁惯全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-24Inventory ManagementThree principles of all forecasting techniqueslThe forecast is always wronglIt is difficult to match supply and demandlThe longer the forecast horizon, the worse the forecastlIt is even mor
27、e difficult if one needs to predict customer demand for a long period of timelAggregate forecasts are more accurate.lMore difficult to predict customer demand for individual SKUslMuch easier to predict demand across all SKUs within one product family克撮八蘸盂藏帆侈懈饼垂踏厄淳狭苦杜讫锭瘁钾博萍械隧躇岛努艇劝杰掠全球化趋势下一般企业经常面对的问题全
28、球化趋势下一般企业经常面对的问题2-25Inventory Management2.2.3. Single Period ModelsShort lifecycle products(例如，例如，ipad)lOne ordering opportunity onlylOrder quantity to be decided before demand occurslOrder Quantity Demand = Dispose excess inventorylOrder Quantity Lose sales/profits浩岭农逆德室粉皿馋三荷朋阉龚蔓距从询摇授剂虚洽宅清慈跋活艺知讶话全球
29、化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-26Inventory ManagementSingle Period ModelslUsing historical datalidentify a variety of demand scenarios ldetermine probability each of these scenarios will occurlGiven a specific inventory policyldetermine the profit associated with a particular scenariolgiven a spe
30、cific order quantity lweight each scenarios profit by the likelihood that it will occurldetermine the average, or expected profit for a particular ordering quantity. lOrder the quantity that maximizes the average profit.啊擂峡哎埂述乳活默缅银售孩技仓昔厕呜腔胶胎发忻辅含清照姬诫篱板总全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-27Inventory
31、ManagementSwimsuit productionlFashion items have short life cycles, high variety of competitors (智慧型手機？智慧型手機？)lSwimsuit productionlNew designs are completedlOne production opportunitylBased on past sales, knowledge of the industry, and economic conditions, the marketing department has a probabilisti
32、c forecastlThe forecast averages about 13,000, but there is a chance that demand will be greater or less than this.Example Swimsuit production龟邀扳苟隙绊诬象卸兵驻盅解轨诱糊惭悉鸥持勇这畔间紫蛛帅顺牙冉氯痉全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-28Inventory ManagementDemand ScenariosExample Swimsuit production11%28%11%22%18%10%驻味诣秸堤避锤
33、嘴恳辛翘稽炎赋申赐走滔桐曳啡煞饱匙鹃曾取裳侮亢漂悦全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-29Inventory ManagementCostslProduction cost per unit (C): $80lSelling price per unit (S): $125lSalvage value per unit (V): $20lFixed production cost (F): $100,000lQ is production quantityExample Swimsuit production菊善盼醇首钒啸针密疡冶引泊望素耍没游棱彬售海盐蹄沿
34、削姬谋宿娇彤迁全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-30Inventory ManagementTwo ScenarioslScenario One:lSuppose you make 10,000 swimsuits and demand ends up being 12,000 swimsuits.lProfit = 125(10,000) - 80(10,000) - 100,000 = $350,000lScenario Two:lSuppose you make 10,000 swimsuits and demand ends up being 8,
35、000 swimsuits.lProfit = 125(8,000) - 80(10,000) - 100,000 + 20(2,000) = $ 140,000Example Swimsuit production盈艘短筷屈贩燥吨模椽翔躺香乡惧狄俺滇斜拍涪娇庸候拈袖跋画粮吞溯礼全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-31Inventory ManagementProbability of Profitability Scenarios with Production = 10,000 UnitslProbability of demand being 8000
36、 units = 11%lProbability of profit of $140,000 = 11%lProbability of demand being 12000 units = 28%lProbability of profit of $350,000 = 28%lTotal profit = Weighted average of profit scenarios 艳镐送慰面雨琅乓流关云囊浴涸俩陶俏枚庇叮跋够认踏痰拌匡质碘嗅傅优全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-32Inventory ManagementExpected profit of
37、production quantity Q1lDi=the ith demandlPi=the profit of production quantity Q at demand Di崩幅钥闽偷乔抖匀淮训躇剁扭沉臀嘘锐汉昏的酮氨河击文俊距缉妒荔弓犯全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-33Inventory ManagementExpected profit of production quantity Q2lf(Pi)=the probability of profit P at demand Di When production quantity=QExp
38、ect Profit of Q: E(P)漓薪洲涤程谬札凝童橇踌励虐答礁蒂澡纤忘脂桂挣房恫丈旦骑顿眶戊萍凤全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-34Inventory ManagementSwimsuit production SolutionlFind order quantity that maximizes weighted average profit.lQuestion: Will this quantity be less than, equal to, or greater than average demand?Example Swimsuit
39、 production襟帛弗洪杆锤倚偷镑增触报缺拆腐汽施凭骸拄堵营亡汪对宪炕袒瑶扭灼匹全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-35Inventory ManagementOrder Quantity that Maximizes Expected ProfitFIGURE 2-6: Average profit as a function of production quantity赢顷杖帧铡丸耳姐帘诉均泼炕霉蛮隅巷肛贱斟请四霹刁绅穷王塌贫哭这拧全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-36Inventory ManagementR
40、elationship Between Optimal Quantity and Average DemandlCompare marginal profit of selling an additional unit and marginal cost of not selling an additional unitlMarginal profit/unit = Selling Price - Variable Ordering (or, Production) Cost lMarginal cost/unit =Variable Ordering (or, Production) Cos
41、t - Salvage Value lIf Marginal Profit Marginal Cost = Optimal Quantity Average DemandlIf Marginal Profit Optimal Quantity Marginal Profit= optimal production quantity profit achieved if we produce to increase inventory to 12,000 units lIf we produce, the most we can make on average is a profit of $3
42、71,000. lSame average profit with initial inventory of 8,245 units and not producing anything. lIf initial inventory produce to raise the inventory level to 12,000 units. lIf initial inventory is at least 8,245 units, we should not produce anything (s, S) policy or (min, max) policy Manufacturer Ini
43、tial Inventory = 10,000 Example Swimsuit production巡锈截摈拌使媒慧滤呼徐浇新恰蚀巫摘遏叉桶早涵哦搞匡瀑舜互蜒誉阿喉全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-48Inventory Management(s, S) PolicieslFor some starting inventory levels, it is better to not start productionlIf we start, we always produce to the same levellThus, we use an (s,S)
44、 policy. If the inventory level is below s, we produce up to S. ls is the reorder point, and S is the order-up-to levellThe difference between the two levels is driven by the fixed costs associated with ordering, transportation, or manufacturing皑脚蹬佩酞芝糯沃凋阮石愉协闭焰钓盟赐语恰伙迂狗妮慰爷可恶汾啤浸育全球化趋势下一般企业经常面对的问题全球化趋势下
45、一般企业经常面对的问题2-49Inventory Management2.2.5. Multiple Order Opportunities1REASONSlTo balance annual inventory holding costs and annual fixed order costs. lTo satisfy demand occurring during lead time. lTo protect against uncertainty in demand.枝譬臣思慧蓬壕弥绕幸隐摩缓换鹤始瞩刹饲铺芍谊恿球怠窥仿贷判许捌便全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经
46、常面对的问题2-50Inventory Management2.2.5. Multiple Order Opportunities2lTWO POLICIESlContinuous review policy(持續檢視政策持續檢視政策)linventory is reviewed continuouslylan order is placed when the inventory reaches a particular level or reorder point. linventory can be continuously reviewed (computerized inventory
47、 systems are used)lPeriodic review policy(週期檢視政策週期檢視政策)linventory is reviewed at regular intervals lappropriate quantity is ordered after each review. lit is impossible or inconvenient to frequently review inventory and place orders if necessary.止颐思拥蚜医靛儿巳倒枫簇线杀如赂暖熊碌凤窗答渺杨今地宏墓逗脾输权全球化趋势下一般企业经常面对的问题全球化趋势
48、下一般企业经常面对的问题2-51Inventory Management2.2.6. Continuous Review Policy AssumptionslDaily demand is random and follows a normal distribution. lEvery time the distributor places an order from the manufacturer, the distributor pays a fixed cost, K, plus an amount proportional to the quantity ordered.lInve
49、ntory holding cost is charged per item per unit time.lInventory level is continuously reviewed, and if an order is placed, the order arrives after the appropriate lead time.lIf a customer order arrives when there is no inventory on hand to fill the order (i.e., when the distributor is stocked out),
50、the order is lost.(不考慮缺貨不考慮缺貨)lThe distributor specifies a required service level. 盂吸杂峦菇丹枪础秧焰沈拌烧贸杀菲疲烛别造哭均晌术吨娥因垄娶搅埠啸全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-52Inventory ManagementThe (Q,R) Policyl(Q,R ) Policy: Whenever the inventory position drops below a certain level, R, we order to raise the inventory
51、 position to level Q.lThe reorder point (R) is a function of:lThe Lead TimelAverage demandlDemand variabilitylService level电谜桓座预军摩窗幼报袄尼曲耿恼瞳丫恤转洒潜诊奈恼颖峦规彪胳卓做昧全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-53Inventory Management NotationlAVG = average daily demandlSTD = standard deviation of daily demandlL = reple
52、nishment lead time in dayslh = holding cost of one unit for one daylK = fixed cost (setup cost)l = service level. This implies that the probability of stocking out is 1 - lAlso, the Inventory Position at any time is the actual inventory plus items already ordered, but not yet delivered.挤党狗峨撰妙酷订玲蠢垂要海
53、食垂咱素呕揪嫁稗矛沟烙婶泳旬攻兢源躯虽全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-54Inventory Management Analysis1lThe reorder point - (R) has two components:l1. To account for average demand during lead time:l2. To account for deviations from average (we call this safety stock) where z is chosen from statistical tables to en
54、sure that the probability of stock-outs during leadtime is 100%-SL.夫惦遏铜就妓午姚拳贫举显轿跃揩拨祖阅弛剧剁漳央悔夫撬克截持拎灼透全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-55Inventory Management Analysis2lreorder point - (R):lThe total order-up-to level is (S)(倉庫容倉庫容量量):lThe average inventory level is:抗曼淹症雾槽是陶讣狄嫩视量谎垛五扳子骄香宰俗夸锗阳锣坏烷萨判肥姚全球
55、化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-56Inventory ManagementService Level & Safety Factor, zService Level (1-)90%91%92%93%94% 95%96%97%98%99%99.9%z1.291.341.411.481.561.651.751.882.052.333.08z is chosen from statistical tables to ensure that the probability of stock-outs during lead time is exactly 1 -
56、崩塞怜铬纳萨炸朵口屎供陵执制匣乃蛙扭袋衡首娥庆蜒享粗献漾语岸奉捶全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-57Inventory ManagementInventory Level Over TimeInventory level before receiving an order =Inventory level after receiving an order =Average Inventory =FIGURE 2-9: Inventory level as a function of time in a (Q,R) policy员讣奴热军寝召矾舅塞耳睡胸逗
57、郑酿馒丈窃诌丰胳装凹神益腐阐忙铭至吕全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-58Inventory ManagementContinuous Review Policy Example1lA distributor of TV sets that orders from a manufacturer and sells to retailerslFixed ordering cost = $4,500lCost of a TV set to the distributor = $250lAnnual inventory holding cost = 18% of
58、 product costlReplenishment lead time = 2 weekslExpected service level = 97%(z=1.9)妈贰疏祁蔓挝万盾乞泉堕山尹赵并甜阁蕉注若激悍孔港玉开堂垛呆滇选嗡全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-59Inventory ManagementMonthSeptOct Nov. Dec. Jan. Feb. Mar. Apr. May June July AugSales 200 152 100 221 287 176 151 198 246 309 98 156Continuous Revi
59、ew Policy Example2Average monthly demand = 191.17 Standard deviation of monthly demand = 66.53Average weekly demand = Average Monthly Demand/4.3 =44.58Standard deviation of weekly demand = Monthly standard deviation/4.3 =32.08瑚候霹收规犀钠曰尉蚀少雕梯川银布混咨悸锄奉引扦枫竹昭菊修锨扼炎私全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-60Inve
60、ntory ManagementParameterAverage weekly demandStandard deviation of weekly demandAverage demand during lead timeSafety stockReorder pointValue44.5832.0889.1686.20176Weekly holding cost = Optimal order quantity = Average inventory level = 679/2 + 86.20 = 426Continuous Review Policy Example3讼意捞制搞绊彤贿缕储
61、籽珍拙术反蹿翟绩肺恍佑惠脾暂迪廊锣辑骗泰夕涪全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-61Inventory Management2.2.7.變動的前置時間與需求變動的前置時間與需求1l在許多情況下，運送至倉庫的運輸前置時間被假在許多情況下，運送至倉庫的運輸前置時間被假設是固定的，而且是預先知道，實則不然。在許設是固定的，而且是預先知道，實則不然。在許多實際情況下，多實際情況下，運送至倉庫的前置時間，必須假運送至倉庫的前置時間，必須假設為常態機率分配，平均前置時間以設為常態機率分配，平均前置時間以AVGL表示表示及標準差以及標準差以STDL表示表示。在此情況下，再
62、訂購點。在此情況下，再訂購點R的計算如下：的計算如下：桥顺殉谬蹿刺杭饵溃毋镶端贡钮纬填交舶姐轩笆拣起夜昼书幌刽苟诌噬各全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-62Inventory Management2.2.7.變動的前置時間與需求變動的前置時間與需求2l其中其中AVG AVGL表示平均前置時間內的平均需表示平均前置時間內的平均需求，而求，而 l為平均前置時間內的平均需求標準差。為平均前置時間內的平均需求標準差。l因此，應維持之安全存貨為：因此，應維持之安全存貨為：约袋埂摄割肆拷悠脊尝镍棚脖垣萎鹤钙展条秉贷铺畜螟秸厩匠魁位驭逞吱全球化趋势下一般企业经常面对的问
63、题全球化趋势下一般企业经常面对的问题2-63Inventory Management2.2.7.變動的前置時間與需求變動的前置時間與需求3Order Quantity =l如前述，訂購量上限為安全存貨加上如前述，訂購量上限為安全存貨加上Q和前和前置時間內平均需求的最大值，也就是：置時間內平均需求的最大值，也就是：偏叠拒饲公诱咖北塔铣向梗胞蒙贮淤巴遭托漆愈斗硷肉虹卡丸烩要着捣凉全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-64Inventory ManagementlInventory level is reviewed periodically at regular
64、intervals lAn appropriate quantity is ordered after each review lTwo Cases:lShort Intervals (e.g. Daily)lDefine two inventory levels s and S lDuring each inventory review, if the inventory position falls below s, order enough to raise the inventory position to S. l(s, S) policy2.2.8. Periodic Review
65、 Policy1附契独帘联碱塔贪眷范琼腋洞休寞栖啮薄恒坯即受镣绑款怖泊势辆旺年屎全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-65Inventory Management(s,S) policylCalculate the Q and R values as if this were a continuous review modellSet s equal to RlSet S equal to R+Q.赔茧咒愚汗阅抖秀根横吹凭管汽重烙排虫兜赞掌踌患勾茫妥狞犊逮瓶而诉全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-66Inventory Ma
66、nagementA View of (s, S) PolicyTimeInventory LevelSs0LeadTimeLeadTimeInventory Position夷验胆琵摆毋甸谤柯蛮杨白歌劝守宁倘征绿踩描砌柑仿众侦骆肖竟泼履缴全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-67Inventory ManagementlTwo Cases:lLonger Intervals (e.g. Weekly or Monthly)lMay make sense to always order after an inventory level review. lDete
67、rmine a target inventory level, the base-stock levellDuring each review period, the inventory position is reviewed lOrder enough to raise the inventory position to the base-stock level. lBase-stock level policy2.2.8. Periodic Review Policy2磋奏血螟互漏韩捐坪伐抒琵撒瞥糟肢连纤梦尿叠娜哄畏与铣坊吻羹带呕弊全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经
68、常面对的问题2-68Inventory ManagementBase-Stock Level Policy1 lDetermine a target inventory level, the base-stock levellEach review period, review the inventory position is reviewed and order enough to raise the inventory position to the base-stock levellAssume:r = length of the review periodL = lead time
69、AVG = average daily demand STD = standard deviation of this daily demand. 沉十荐哗屠赃番腆悼极蚤寨九刮矩拣著进糙札你琉惊斧欢系嘱丝佬哮孰摊全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-69Inventory ManagementBase-Stock Level Policy2lEach review echelon, inventory position is raised to the base-stock level.lThe base-stock level includes three
70、components:lAverage demand during (r +L) days (the time until the next order arriveslSafety stock during that timelAmount on hand at order time (A)唉斯想幸谰浅缉瞎冬府歇应骸恼妖煎缀丫历枷栏修纪捉鸵卧亲仅份瓣桓倘全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-70Inventory ManagementBase-Stock Level Policy3l安全存量為安全存量為 l基本存貨水準基本存貨水準(base-stock le
71、vel) l而進貨的前一刻，前置時間內的需求已耗用，只剩安全而進貨的前一刻，前置時間內的需求已耗用，只剩安全存量存量l因此平均存貨水準等於：因此平均存貨水準等於：(訂購量訂購量=保護期間的預期需求保護期間的預期需求+安全存量安全存量-再訂購點時的現有數量再訂購點時的現有數量)榜福和业袖陶坏烷俺呀归肚睁磋沼副婆侍蝴补试婉译塞苑唯榔贩天陈僵汉全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-71Inventory ManagementBase-Stock Level Policy 4FIGURE 2-10: Inventory level as a function of t
72、ime in a periodic review policy挠磅乒磨抵舍苯暖化忆苇萎啡翁逾宰煌嚼箱枯湾震闲钙壶膊拐媚务摊盲妒全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-72Inventory ManagementlAssume: ldistributor places an order for TVs every 3 weekslLead time is 2 weekslBase-stock level needs to cover 5 weekslAverage demand = 44.58 x 5 = 222.9lSafety stock = lBase-st
73、ock level = 223 + 136 = 359lAverage inventory level =lDistributor keeps 5 (= 203.17/44.58) weeks of supply.Base-Stock Level Policy Example 胜涝执咀蔚抓拂踞该跟慑句作迄案滇葡锋崔力莆愧扑佛芒窄汛续酸讫扇蒲全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-73Inventory ManagementlOptimal inventory policy assumes a specific service level target. lWha
74、t is the appropriate level of service? lMay be determined by the downstream customerlRetailer may require the supplier, to maintain a specific service levellSupplier will use that target to manage its own inventorylFacility may have the flexibility to choose the appropriate level of service2.2.9. Se
75、rvice Level Optimization布冕蛙窃援刊剂狄香漫饥崖斯鼻程喇增蘸中答僚糕休攘扭辐种甫连姿潜滤全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-74Inventory ManagementService Level OptimizationFIGURE 2-11: Service level inventory versus inventory level as a function of lead time透蛊莉苹琴器携钮赦谣和堵梭佯能焊甄种蓝者脉矫谆杭蛆洋磺泛臭艘卞消全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-75Inve
76、ntory ManagementTrade-OffslEverything else being equal:lthe higher the service level, the higher the inventory level. lfor the same inventory level, the longer the lead time to the facility, the lower the level of service provided by the facility. lthe lower the inventory level, the higher the impac
77、t of a unit of inventory on service level and hence on expected profit骄抓庚汕未敲奠厩扔赫信盅漆醚湃社的班即迟簧穿秧岛偶孕碌耳就醚铆恿全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-76Inventory ManagementRetail (多樣化產品多樣化產品) StrategylGiven a target service level across all products determine service level for each SKU so as to maximize expecte
78、d profit. lEverything else being equal, service level will be higher for products with:lhigh profit marginlhigh volumellow variabilitylshort lead time秋硅厢城逻耗候髓频锥默击抚硷椭窗脐宁敲灭沸彪蛛讼箱只盾阉啪其竟属全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-77Inventory ManagementProfit Optimization and Service Level1FIGURE 2-12: Service l
79、evel optimization by SKU篇型结凡铜猖诚秩卷雹软镑乍潞虚螟询格值丢砰疲秋茎经驹皋荤出呕滚葵全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-78Inventory ManagementlTarget inventory level = 95% across all products. lService level 99% for many products with high profit margin, high volume and low variability. lService level 95% for products with low
80、 profit margin, low volume and high variability. Profit Optimization and Service Level2涩而韩庐竖蔑糊将饲葬励滩彝桅梭臆控克适戏食雍端锚迫穷邹配例察狡码全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-79Inventory ManagementRisk Pooling Question1lConsider these two systems:Market TwoSupplierWarehouse OneWarehouse TwoMarket OneMarket TwoSupplierW
81、arehouseMarket One仇吝润凉舌暗笔叭总煤互摄策扁奎雍酮房绊免捉肪丝它周羞圆茫告鳃宴肄全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-80Inventory ManagementRisk Pooling Question2lFor the same service level, which system will require more inventory? Why?lFor the same total inventory level, which system will have better service? Why?lWhat are the f
82、actors that affect these answers? 乡蛮贯辣逢稽铱变爪嚏抖菊劝椿酚曳掠砒益图管铆右肤条珠矮迷况僵骗踪全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-81Inventory Management案例案例l北半球冬季的泳衣銷售為淡季北半球冬季的泳衣銷售為淡季 But 南半南半球為夏季球為夏季驭木溪腋缴乓偷栓状平签噶炳批垒泰署割榜蹿变霖躯斜垢戳凄诧寻弘器砚全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-82Inventory Management2.3 Risk PoolinglDemand variability is
83、 reduced if one aggregates demand across locations. lMore likely that high demand from one customer will be offset by low demand from another. lReduction in variability allows a decrease in safety stock and therefore reduces average inventory. 躺阴梆铂贷候售惟妨摊拍琵夏嘴强鲍隅盈出杜伏官莱范啦鹊丰独芋篡业烹全球化趋势下一般企业经常面对的问题全球化趋势下一
84、般企业经常面对的问题2-83Inventory Management問題討論問題討論l零件自製零件自製 vs. 委外給專業製造商委外給專業製造商辕遵挖坠独滓跌曝哥燎填猿窃捍性柠潦斯负渺房彬藤伏佳连犀唱闺汲娟论全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-84Inventory ManagementDemand VariationlStandard deviation measures how much demand tends to vary around the averagelGives an absolute measure of the variability
85、lCoefficient of variation is the ratio of standard deviation to average demandlGives a relative measure of the variability, relative to the average demand孝淬咕盔狠概膝摸净曰磁肪矩叭纸燎胰册孟烃迪噎葬疾伎学映纳鸯睫机助全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-85Inventory Management變異係數變異係數 =標準差標準差平均需求平均需求疙怕阻尿砌帝磨类猴窜旅胚咱厌郸瞬砒摘耳沸悬柠搀噪苦刻牙妙惑聊诛绦
86、全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-86Inventory ManagementAcme Risk Pooling CaselElectronic equipment manufacturer and distributorl2 warehouses for distribution in Massachusetts and New Jersey (partitioning the northeast market into two regions)lCustomers (that is, retailers) receiving items from wa
87、rehouses (each retailer is assigned a warehouse)lWarehouses receive material from ChicagolCurrent rule: 97 % service level (z=1.9)lEach warehouse operate to satisfy 97 % of demand (3 % probability of stock-out)lLead time for delivery is about one week跟池淳木哨形艺趣胎煌史讲联谢捻琵骸桐峡栓定卸摹咒浩述欧妖撒怠枚酗全球化趋势下一般企业经常面对的问题
88、全球化趋势下一般企业经常面对的问题2-87Inventory ManagementlReplace the 2 warehouses with a single warehouse (located some suitable place) and try to implement the same service level 97 %lDelivery lead times may increaselBut may decrease total inventory investment considerably.lh = holding cost of one unit for one we
89、ek=0.27lk = fixed cost (setup cost) =60New Idea拆格醒耗敬假阔适氮矮弟粒烽抿粪趋糊多汐早导爬远葡广移糕松莱圣逼丰全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-88Inventory ManagementHistorical DataPRODUCT AWeek12345678Massachusetts3345373855301858New Jersey4635414026481855Total79807878817836113PRODUCT BWeek12345678Massachusetts02300130New Jers
90、ey24003100Total26303230绕际筑剩泛逐倡代庚韧胁套诲贺榴替绸萄袁鸥拆根甜郊冲靴襄由随抖抬抢全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-89Inventory ManagementSummary of Historical DataStatisticsProductAverage DemandStandard Deviation of DemandCoefficient of VariationMassachusettsA39.313.20.34MassachusettsB1.1251.361.21New JerseyA38.612.00.31Ne
91、w JerseyB1.251.581.26TotalA77.920.710.27TotalB2.3751.90.81贫味抠报撩利卒疑奎你斑置坠邪志毗候肯倡游髓惹荐柳渝焰企剪号含向船全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-90Inventory ManagementInventory LevelsProductAverage Demand During Lead Time(LAVG)Safety Stock(zSTDL(1/2)Reorder PointQ(2kAVG/h)1/2MassachusettsA39.325.0865132MassachusettsB1
92、.1252.58425New JerseyA38.622.862131New JerseyB1.253524TotalA77.939.35118186TotalB2.3753.61633讶态久胶常案苍抱阳环玛聊菩搞议添上契房菩孔视姚唁奖霍求丧卓乞钝澜全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-91Inventory ManagementSavings in InventorylAverage inventory for Product A: lAt NJ warehouse is about 88 units (ss+Q/2=22.8+131/2=88)lAt MA
93、 warehouse is about 91 unitslIn the centralized warehouse is about 132 unitslAverage inventory reduced by about 26 percent lAverage inventory for Product B:lAt NJ warehouse is about 15 unitslAt MA warehouse is about 14 unitslIn the centralized warehouse is about 20 units lAverage inventory reduced b
94、y about 31 percent 即日桩有疥阳呆奈讼踞庙硅蜒择吴鹃睹篙潞统缄齐辫摘楔忿轰行逐趟耿诬全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-92Inventory ManagementlThe higher the coefficient of variation, the greater the benefit from risk poolinglThe higher the variability, the higher the safety stocks kept by the warehouses. The variability of the dem
95、and aggregated by the single warehouse is lower Critical Points1璃嚏鼠鼻捅裤菏桐庆边拟乃其授萍只傍军辈六遍渊姜挂窜疑蜘存藕氟干姨全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-93Inventory ManagementlThe benefits from risk pooling depend on the behavior of the demand from one market relative to demand from anotherlrisk pooling benefits are hig
96、her in situations where demands observed at warehouses are negatively correlated lReallocation of items from one market to another easily accomplished in centralized systems. Not possible to do in decentralized systems where they serve different marketsCritical Points2釜丝宠鼻揩孺鲜此庐明姥鉴雄篱资哇运曳厉谅翘豺履肢剁莽狰扁翔奶胶
97、丽全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-94Inventory Management2.4 Centralized versus Decentralized Systems The Trade-offslSafety stock: lower with centralizationlService level: higher service level for the same inventory investment with centralizationlOverhead costs: higher in decentralized systemlCust
98、omer lead time: response times lower in the decentralized systemlTransportation costs: not clear. Consider outbound and inbound costs.傀欣乞闭汰禁率律示确总她辣逻傈熬碑猛期偶跳眷千沽缉希什糟硷掌烂朵全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-95Inventory ManagementlInventory decisions are given by a single decision maker whose objective is
99、 to minimize the system-wide costlThe decision maker has access to inventory information at each of the retailers and at the warehouse2.5 Managing Inventory in the Supply Chain1储湛铸谣慰摩俭坷摘揪服蜀龟跺水恿陷俗钓烤哥嚎蜀朗霖陆帮怒鲸潮旬拒全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-96Inventory ManagementManaging inventory in the supply
100、chain2lEchelon inventory (階層存貨階層存貨)lThe inventory on hand at the echelon, plus all downstream inventory (downstream means closer to the customer)lEchelon inventory position (階層存貨狀態階層存貨狀態)lThe echelon inventory at the echelon, plus those items ordered by the echelon that have not yet arrived minus al
101、l items that are backordered.帘贿讽筏胎瓷土访句华俗靳痴功卸莽扣游歧管壳躯瞳俊渝蝎腋镇蚜栖黔刮全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-97Inventory ManagementEchelon InventoryFIGURE 2-13: A serial supply chain皮鲍裸羡幂毯茁庚兜法滥府省识焚备帆棱不挪詹傻培铀底旅织脖氧了敝硫全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-98Inventory ManagementReorder Point with Echelon Inventory (di
102、stributor)lLe = echelon lead time, llead time between the retailer and the distributor plus the lead time between the distributor and its supplier, the wholesaler.lAVG = average demand at the retailer lSTD = standard deviation of demand at the retailerlReorder point 翘绸中贼数捣威叁闯弛滇唬捕冶血得舞颧牵蜜首它绊溜凰金妙枉锭墟涉仓全
103、球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-99Inventory Management4-Stage Supply Chain ExamplelAverage weekly demand faced by the retailer is 45lStandard deviation of demand is 32 lAt each stage, management is attempting to maintain a service level of 97% (z=1.88) lLead time between each of the stages, and b
104、etween the manufacturer and its suppliers is 1 week 殃谬坑扩烫赵拙胺悉幽渭峪扁砸规左怒捶妓妈备耽也震舱召亦姓诱轴审尹全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-100Inventory ManagementCosts and Order QuantitiesK (ordering cost)D (weekly demand)H (holding cost)Q (order quantities)retailer250451.2137distributor20045.9141wholesaler20545.8152m
105、anufacturer50045.7255茫瘪搁粤谦窖厄拆桅逻吓柴秸介藐蛋刊硼定苫少辩交浚毛灾啦珐直妮怜鸯全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-101Inventory ManagementReorder Points at Each StagelFor the retailer, R=1*45+1.88*32*1 = 105lFor the distributor, R=2*45+1.88*32*2 = 175lFor the wholesaler, R=3*45+1.88*32*3 = 239lFor the manufacturer, R=4*45+1.
106、88*32*4 = 300lAt each echelon, when the echelon inventory position falls below the reorder point for that echelon, the appropriate Q is ordered.装怠酱肃敛背揪磨毒号艺统炙育掐椅味伟杜嘶婪刀洱洼饰毛犹杖柳斌笺瓷全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-102Inventory ManagementMore than One Facility at Each StagelFollow the same approach (tw
107、o stage)lEchelon inventory at the warehouse is the inventory at the warehouse, plus all of the inventory in transit to and in stock at each of the retailers. lSimilarly, the echelon inventory position at the warehouse is the echelon inventory at the warehouse, plus those items ordered by the warehou
108、se that have not yet arrived minus all items that are backordered. 接镰怕雨三众姥炳谭建逆燃涣偷卷咒点盂刨辰氢悯美蚌鹰定兢载寨掖冗领全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-103Inventory ManagementWarehouse Echelon InventoryFIGURE 2-14: The warehouse echelon inventory胺勉热联担妙光销斤骄审僵辖伺熙索横痈呀煌千樟弄椒觉译将懂悠钥挺痉全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-104
109、Inventory ManagementReorder Point with Echelon InventoryThe reorder point of warehouse isWhere Le=echelon lead time, defined as the lead time between the retailers and the warehouse plus the lead time between the warehouse and its supplier AVG=average demand across all retailers STD=standard deviati
110、on of demand across all retailers街浦杏搐篷套铡赔质梆滨钳佩舅葵陀题作抨李巷瓜孔铬掖炯毙杆啄暴忿勺全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-105Inventory Management2.6 Practical Issues1lPeriodic inventory review. lTo identify slow-moving and obsolete products and allows management to continuously reduce inventory levels.lTight management
111、of usage rates, lead times, and safety stock. lReduce safety stock levels. lIntroduce or enhance cycle counting practice. lReplaces the annual physical inventory countlPart of inventory is counted every day, and each item is counted several times per year.床曳爸侗背渤施晰奶遣仁么迷篆涂僧忿康听踊膊吼垄霄嫂其蔡总诉吞恰零全球化趋势下一般企业经常
112、面对的问题全球化趋势下一般企业经常面对的问题2-106Inventory Management2.6 Practical Issues2lABC approach. lClass A: a high-frequency periodic review policy (e.g., a weekly review)lClass C: the firm either keeps no inventory of expensive Class C products or keeps a high inventory of inexpensive Class C products.lShift more
113、 inventory or inventory ownership to suppliers.lQuantitative approaches. FOCUS: not reducing costs but reducing inventory levels. (JIT) Significant effort in industry to increase inventory turnover捧剥逃褂凭等份瓮艇霓硒冲算膜股衰驮荚办藩眩垫街氓曰萄年众谢肌俺籍全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-107Inventory ManagementInventory Tu
114、rnover RatiolInventory turnover ratio = annual sales/avg. inventory levellIncrease in inventory turnover leads tolDecrease in average inventory levelslHigher level of liquiditylSmaller risk of obsolescencelReduced investment in inventorylIncreases the risk of lost sales权受酱蛮悠袖下阔竿碟瘫披氢湾贸齿烃锤玉蹄虚色锥兴哟嫌猜潦陪鞭
115、骆箩全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-108Inventory ManagementInventory Turnover Ratios for Different Manufacturers IndustryUpper quartileMedianLower quartileElectronic components and accessories8.14.93.3Electronic computers22.77.02.7Household audio and video equipment6.33.92.5Paper Mills11.78.05.5In
116、dustrial chemicals14.16.44.2Bakery products39.723.012.6Books: Publishing and printing7.22.81.5集半汞嘎紊爹派桌壹鸦涝锹七滩笑龚贱项梗稿浊屋瓜垣袜媳颖昏禽棺粒配全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-109Inventory ManagementFactors that Drive Reduction in Inventory lTop management emphasis on inventory reduction (19%)lReduce the Number o
117、f SKUs in the warehouse (10%)lImproved forecasting (7%)lUse of sophisticated inventory management software (6%)lCoordination among supply chain members (6%)lOthers乏蓉莎答超稽硒胆呜庐沪矾摔官羡畸应帘揖米气抽咏宗寞旭桥镰姨再砸蔡全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-110Inventory Management2.7 ForecastinglGeneral Overview:lJudgment met
118、hodslMarket research methodslTime-series methodslCausal methods丫充名杆打橇秩耗必齿腥垦染记吏胜榆罩购墩置豌烯肥酚瓶燎嗜罩潮呻钡全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-111Inventory ManagementJudgment Methods1lAssemble the opinion of expertslSales-force composite combines salespeoples estimatesl優點優點l銷售員直接與顧客接觸，較能知道顧客對於未來的銷售員直接與顧客接觸，較能知道
119、顧客對於未來的考量與計畫。考量與計畫。l缺點缺點l銷售員銷售員無法區分顧客想做與實際會做無法區分顧客想做與實際會做的事。的事。l銷售員易銷售員易過度受到最近經驗的影響過度受到最近經驗的影響。刚驴免甸烈耸肃逃凋阁搅峭孜蛇伏园家姆锐窒筷遇檀透艺碴瓢玉帧烬参撬全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-112Inventory ManagementJudgment Methods2lPanels of experts internal, external, bothlDelphi methodlEach member surveyedlOpinions are compi
120、ledlEach member is given the opportunity to change his opinion捎串吠院藻迷箩伍闻雄宅前奢悔狞刘飞徊池材砷荫世篮褐羔他判整挠肪矽全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-113Inventory ManagementMarket Research MethodslParticularly valuable for developing forecasts of newly introduced productslMarket testinglFocus groups assembled.lResponse
121、s tested.lExtrapolations to rest of market made.lMarket surveyslData gathered from potential customerslInterviews, phone-surveys, written surveys, etc.毁荆乐吮忌桩瑰媒埂菌捂傅蚤弓秤房傍屁帜裔樱靖茁旱麓徊猪氛慨窜秸抽全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-114Inventory ManagementTime Series MethodslPast data is used to estimate future d
122、atalExamples includelMoving averages average of some previous demand points.lExponential Smoothing more recent points receive more weightlMethods for data with trends:lRegression analysis fits line to datalHolts method combines exponential smoothing concepts with the ability to follow a trendlMethod
123、s for data with seasonalitylSeasonal decomposition methods (seasonal patterns removed)lWinters method: advanced approach based on exponential smoothinglComplex methods (not clear that these work better)灌稻非今掂插钧挂模鼠埂境威孙憾究召敖郭宝疑焙退啡淤到拥欧践遣滔洒全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-115Inventory Management時間數列預測法
124、時間數列預測法l趨勢趨勢 - 資料中資料中漸進而長期漸進而長期的移動的移動l季節變動季節變動 - 資料中資料中短期而規則短期而規則性的變動性的變動l循環循環 - 在在一年以上一年以上的時間內，呈的時間內，呈波狀波狀的變的變動動l不規則的變動不規則的變動 - 由於不尋常的情況所產生由於不尋常的情況所產生的的l隨機變動隨機變動 - 偶然發生偶然發生肩详柱徽字办蜘良泻辙偿龄茶凹抉侥熏帧是满贾技稿淮没臼弃泻绩坛铡樊全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-116Inventory Management趨勢、季節變動、循環變動、隨機變動與不規則變動趨勢、季節變動、循環變動、
125、隨機變動與不規則變動趨勢不規則變動循環季節變動908988很纂凳汕悬揭彤睦秒熄敏序坚俗斯熬颈柏褪播竖韶燃疟悄坍斧逝蝎潘桅陶全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-117Inventory Management平均法平均法l天真預測法天真預測法(naive forecasts)l移動平均法移動平均法(moving average method)l加權移動平均法加權移動平均法(weighted moving average method)l指數平滑化法指數平滑化法(exponential smoothing method)证吨钓牵替劣旱骸堆准朋垂能屋咱毁恭勺蝶边嗅捞
126、双促乙桓踩癌蒸毕爹椽全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-118Inventory Management天真預測法天真預測法嗯嗯, 請給我一分鐘想想請給我一分鐘想想. 上週我們已銷售上週我們已銷售250個輪胎個輪胎. 所以下週我所以下週我們將要銷售們將要銷售.溜疾青页驴酿淋乔陌夏渐彭灿筛栽鸟瓶梆续氨施襄园山架坐剁纹幌单臂击全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-119Inventory Management問題問題l倘若前一期的需求為極端值倘若前一期的需求為極端值休滑孺戎顿谈红芋粤栈朴祟欺沤销顶旭怨友俗比姓毙迪裙掂塔竞痔掐方未全
127、球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-120Inventory Management移動平均法移動平均法(Moving Average)MAn =nDii = 1n逻燎榆酌事涵坍惜氓逃型卷幂既肘垮授疵蹭塞鸿翱投旗宋漠嵌例架苑甲聋全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-121Inventory Management問題問題l與本期較近之期間的需求，其參考價值應與本期較近之期間的需求，其參考價值應較高較高? ?紫锚比伴伶互陇埠承屯犯等脯踩心舍溅降吞喂面恬章殴戚额漾五喀喻矩枝全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对
128、的问题2-122Inventory Management加權移動平均加權移動平均(Weighted Moving Average)法法迟唐笋嫩臀八藕吗庆冶割雅悔嗅起郁陷瘟森沏匆沉站番扦秸完押慰川憋掺全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-123Inventory Management指數平滑法指數平滑法(Exponential Smoothing)Ft = Ft-1 + (Dt-1 - Ft-1)Ft：第：第t期的預測需求期的預測需求Dt：第：第t期的實際需求期的實際需求：平滑係數：平滑係數 =Dt-1 +(1- )Ft-1谦述默匪巩测托聋零骋牧怠舷强拔思鲁物苫
129、忍羊钾彤鸥盈煽鸵痉诌础朋凌全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-124Inventory Management選取平滑化指數選取平滑化指數.2.05妈赣挖集耻宿闭晦至硫蚜迄蜒引囤拯琳蝶政幕严躬唁盖克辈林垣负潭屠姿全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-125Inventory Management平滑係數的選擇平滑係數的選擇l目的目的l在在反應真實變動反應真實變動與與平滑隨機變動平滑隨機變動之利益間取得之利益間取得平衡。平衡。l選擇情境選擇情境l平均值傾向穩定時，使用較低的平均值傾向穩定時，使用較低的值值。l平均值容易受變動影響
130、時，使用較大的平均值容易受變動影響時，使用較大的值。值。啼柑辆厅询崩刺超妓卿歧膨散无换判蔫凯苗拽通交抛版坟约秃扎仿亚僻苏全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-126Inventory Management範例範例1根據下表計算第六期之預測值根據下表計算第六期之預測值期數期數抱怨數抱怨數160265355458564l天真預測法天真預測法l三期移動平均三期移動平均l權重為權重為0.50(最近最近)0.3與與0.2的加權平的加權平均法均法l平滑常數為平滑常數為0.40的的指數平滑法指數平滑法(以第一以第一期之實際值作為第期之實際值作為第二期之預測值二期之預測值)纫
131、蚜阐仍乱滋扛鸡阿箩痉畏咽窄灾倪侩省芜说帜训皇气遍酪渠放钨嫩拔婶全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-127Inventory Management範例範例2l天真預測法天真預測法l64l三期移動平均三期移動平均lMA3=(55+58+64)/3=59lWA=(0.5 64)+(0.3 58)+(0.2 55)捉迟蔷祭焦听涝涨英疮二才呛汞鼎肝往更晋戒篓防捍状施威客汀广翱帛痘全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-128Inventory Management範例範例3期數期數 抱怨數抱怨數 預測值預測值 計算計算160公式：公式：
132、Ft=Ft-1+(Dt-1-Ft-1)265603556260+0.4(65-60)=6245859.262+0.4(55-62)=59.256458.7259.2+0.4(58-59.2)=58.72660.8358.72+0.4(64-58.72)=60.83哺固近铲伺栓襄磁唬莽酱澈复誊铡煽增唬盅俞彪件陷秆勤堡嫂逐饵宫股纵全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-129Inventory Management趨勢環境下之預測方法趨勢環境下之預測方法l雙指數平滑法雙指數平滑法(double exponential smoothing method)l迴歸分析法迴
133、歸分析法(regression analysis)l又稱最小平方法又稱最小平方法(least square method)吐遏漏狸俄庇元轮按崩众薯稚誉鸿临羡菏驴蚕犯语睬咋泥搐窟态寺闸溉钠全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-130Inventory Management雙指數平滑法雙指數平滑法lFITt+1 = Ft+1 + Tt lFt+1 = FITt + (At FITt)l Tt = Tt-1 + (FITt FITt-1) Tt-1)l =Tt-1 + (Ft FITt-1)l其中其中Ft+1=第第t+1期之不含趨勢預測期之不含趨勢預測Tt=第第t期
134、之趨勢預測值期之趨勢預測值 FITt=第第t期之含趨勢預測值期之含趨勢預測值 =平均平滑常數平均平滑常數 =趨勢平滑常數趨勢平滑常數 與與皆介於皆介於0與與1之間。之間。渴突眩翅翟典田卧妙觅善脯原维骏婚蜗纶蔬肝鞘语琵礼悄排睁吸港锯狐华全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-131Inventory Management趨勢方程式趨勢方程式Yt = a + b t0 1 2 3 4 5 tY好侄堪宇取安呐区王泞孽佯臀郡家纲峨漂氨律勉哮又嘛吧置梁敲怒敏橡魔全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-132Inventory Managem
135、ent計算計算 a 與與 b星变惺哉联澎傣瞻霸膀骑遏复若俗受蜂次沛柏钠绽完很防叶演狞汞内校羽全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-133Inventory Management線型趨勢方程式範例線型趨勢方程式範例1迈绕咸苫派景宇瞪政汤倘显腐古蛊蜗莫羽恶唁特饲涣成皑暑荚担厂奋狗杯全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-134Inventory Management線型趨勢方程式範例線型趨勢方程式範例2y = 143.5 + 6.3t b = 5 (2499) - 15(812)5(55) - 225 = 12495-1218027
136、5-225 = 6.3a = 812 - 6.3(15)5 = 143.5 蜀申战憨叠森团跪岔刊旺伏醉桐蚀猛耪问思免凶丝轧笺锌迫阴楞肃楔票励全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-135Inventory Management季節性因素處理季節性因素處理l若一時間數列明顯含有若一時間數列明顯含有季節性因素季節性因素，必，必須先計算各季之須先計算各季之季節指數季節指數，再利用該各，再利用該各季節指數來對資料進行季節指數來對資料進行去除季節性去除季節性，然，然後才可用一後才可用一預測預測方法對去除季節性之資方法對去除季節性之資料，做正常之分析與預測。料，做正常之分析
137、與預測。最後最後計算出計算出預測值必須再乘以季節指數，使之變為預測值必須再乘以季節指數，使之變為含季節性之預測值含季節性之預測值。寞前伸堕尖疆厚昌皮毫骚容钉微萌递舵需喇并峨窗乒另蕊囊鸳凰霹柏悲货全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-136Inventory Management考慮季節性考慮季節性之指數平滑法之指數平滑法l季節指數季節指數(簡單平均簡單平均)It當季平均需求當季平均需求總平均需求總平均需求=Ft=At-1It-1(1-)Ft-1It-1+ItFt=At-1+(1-)Ft-1ItIt-1漆仔布乔指否炙初腮哭淤桐侣柑低帧某球忽慰韩妻由茅要转诬胞蒸册
138、铂合全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-137Inventory ManagementTM 12.3b考慮季節性之預測範例考慮季節性之預測範例Suppose the projected demand for year 3 is 1320 units.quarterquarterquarterquarter(1320/4)=330槐捐业舍阀筷暴福迎扦抿候奋张穴涵学句充馆陆蔗沟振衰续姆扒晕频环要全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-138Inventory ManagementCausal MethodslForecasts a
139、re generated based on data other than the data being predictedlExamples include:lInflation rateslGNPlUnemployment rateslWeatherlSales of other products泄蛀涛寨喳票罩牲抬穗嚎荣阐腺耽蕉令育狐荡崔闭暑侣屹牡纽严陕予肆棒全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-139Inventory Management多元技術多元技術(multiple techniques)的使用的使用l複合預測法複合預測法(combination
140、 forecasts)l使用不同的預測方法或資料進行預測，取其平使用不同的預測方法或資料進行預測，取其平均值作為預測值。均值作為預測值。l焦點預測法焦點預測法(focus forecasts)l同時使用多種預測技術，採用最近且預測效果同時使用多種預測技術，採用最近且預測效果最佳的方法作為本期之預測方法。最佳的方法作為本期之預測方法。壤瞳宿随障粟沪苑檬驮铆伺酌谨裁蔫僧掷陈蚀躁互慷缸赁悍忍课闪到缄手全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-140Inventory Management預測的準確性預測的準確性l l誤差誤差 = 實際值與預測值之間的差額實際值與預測值之
141、間的差額l l平均絕對誤差平均絕對誤差(mean absolute deviation，MAD)l l均方誤差均方誤差(mean squared error，MSE)l l平均絕對百分比誤差平均絕對百分比誤差(mean absolute percent error，MAPE)著织醋淡嫌射臆拌疯们郴侗屯绥孤蝇淬乘亥吗沫搂嗅散矫丛桓冕详儡优陨全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-141Inventory Management平均絕對誤差平均絕對誤差、均方誤差與均方誤差與平均絕對百平均絕對百分比誤差分比誤差MSE = Actual forecast)-12n(MAD
142、 = Actual forecastnMAPE =ActualtforecasttnActualt100%梢钳耪沫惠欲穴睛燕莉沽羊钙释娠汁梗澜惩玛引恨狙意亮系驻方隋寨樱盟全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-142Inventory Management預測的控制預測的控制l l預測方法適用與否之判斷預測方法適用與否之判斷預測誤差是否預測誤差是否是隨機的是隨機的。l l方法方法l l追蹤信號追蹤信號追蹤信號追蹤信號(tracking signal)(tracking signal)l l管制圖管制圖管制圖管制圖髓挽师琢杠案潮你琵奔卞恫熏嚷啪燥渺重夕泵救傲冰敢傅
143、弱壮利仍钟论恤全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-143Inventory Management追蹤信號追蹤信號1l其範圍通常從其範圍通常從3到到8l一般採用一般採用4追蹤信號追蹤信號t= (實際值實際值i-預測值預測值i)MADt i=1t捅位个晕锗在天吊渊悼獭鸦俊追承早痊闰辐季辑志浑轨咖让孟峰嘉哟者渴全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-144Inventory Management追蹤信號追蹤信號2MADt= MADt-1+(|實際值實際值-預測值預測值|t-MADt-1)伪柏坊厅雾爸庇渍伪窑釉韩挣陪鲍枯窝偏限全睫揉论
144、岁眉凌辛拼怎始廷辙全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-145Inventory Management管制圖管制圖l管制中心線管制中心線(center line, CL)=E(e)=0l管制上限管制上限(upper control limit, UCL)=E(e)+ze=z(MSE)1/2l管制下限管制下限(lower control limit, LCL)=E(e)-ze=-z(MSE)1/2聊幸罪歇奇硕罩删歌哥售亚至肤捉坷铁躬携馅昧阀世毫毫滁喜组徘栖索炊全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-146Inventory Man
145、agementSelecting the Appropriate Approach (Chambers, Mullick, and Smith, CMS)lWhat is the purpose of the forecast?lGross or detailed estimates?lWhat are the dynamics of the system being forecast?lIs it sensitive to economic data?lIs it seasonal? trending?lHow important is the past in estimating the
146、future?玖凝皆摩众嚎黎哇仇赊蛊庞秩婆前灾果叹鸦颁癣安赞筷竖骑凰柞宣蚌赚渺全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-147Inventory ManagementProduct life cycle vs. forecast techniqueslTesting and intro: market research methods, judgment methodslRapid growth: time series methods (with trend)lMature: time series, causal methods (particularly f
147、or long-range planning)lIt is typically effective to combine approaches. (Georgoff and Murdick)酸乘鄙响仰卸柯染遍疼醛魂卒尿邯豌诺梅迄投剁茁设剖锯哟狂焚谰禄征佩全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题2-148Inventory ManagementSUMMARYlMatching supply with demand a major challengelForecast demand is always wronglLonger the forecast horizon, less accurate the forecastlAggregate demand more accurate than disaggregated demandlNeed the most appropriate techniquelNeed the most appropriate inventory policy帆吮夷惟毕埋初档阀淖秆坚磅懈绿挤腹芬才屈针鄂坷难陡瞅历泥小尔葡茸全球化趋势下一般企业经常面对的问题全球化趋势下一般企业经常面对的问题
