【正文】 Inventory Management 96 Judgment Methods2 Panels of experts – internal, external, both Delphi method – Each member surveyed – Opinions are piled – Each member is given the opportunity to change his opinion Inventory Management 97 Market Research Methods Particularly valuable for developing forecasts of newly introduced products Market testing – Focus groups assembled. – Responses tested. – Extrapolations to rest of market made. Market surveys – Data gathered from potential customers – Interviews, phonesurveys, written surveys, etc. Inventory Management 98 Time Series Methods Past data is used to estimate future data Examples include – Moving averages – average of some prev。 –缺點(diǎn) 銷售員無法區(qū)分顧客想做與實(shí)際會(huì)做的事。 Inventory Management 87 Managing inventory in the supply chain3 Echelon inventory position – The echelon inventory at the echelon, plus those items ordered by the echelon that have not yet arrived minus all items that are backordered. Inventory Management 88 The warehouse echelon inventory1 Supplier Warehouse Retailers Warehouse echelon lead time Inventory Management 89 The warehouse echelon inventory2 The reorder point of warehouse is ees L A V G z S T D L? ? ? ?Where 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 deviation of demand across all retailers Inventory Management 90 Inventory Management: Best Practice Periodic inventory reviews Tight management of usage rates, lead times and safety stock (the smaller variation) ABC approach Reduced safety stock levels Shift more inventory, or inventory ownership, to suppliers Quantitative approaches Inventory Management 91 Inventory Turnover Ratio Inventory turnover ratio = annual sales/avg. inventory level Increase in inventory turnover leads to – Decrease in average inventory levels – Higher level of liquidity – Smaller risk of obsolescence – Reduced investment in inventory – Increases the risk of lost sales Inventory Management 92 Indus tr y Upper Quart ile Medi an Low er Quart ile Dair y Product s Electronic Com ponent Electronic Com puters Books: publis hing Household audio amp。 在配銷系統(tǒng)中，每一階段或?qū)蛹?jí) (亦即倉庫或零售商 )被視為一階層 (echelon)。 2. 決策者有 獲取各零售商和倉庫存貨資訊 的管道。公司的 目的 在 管理其存貨以降低整體系統(tǒng)成本 ；因此 考慮不同設(shè)施間的互動(dòng)及這些互動(dòng)對(duì)每個(gè)設(shè)施應(yīng)採取存貨政策的影響是很重要的。在此情況下，再訂購點(diǎn) R的計(jì)算如下： 其中 AVG AVGL表示平均前置時(shí)間內(nèi)的平均需求，而 為平均前置時(shí)間內(nèi)的平均需求標(biāo)準(zhǔn)差。 (無窮的 ) Inventory Management 13 EOQ: Calculating Total Cost Purchase Cost Constant Holding Cost (h): (Avg. Inven) * (Holding Cost) Ordering (Setup Cost) (k): Number of Orders * Order Cost Goal: Find the Order Quantity that Minimizes These Costs: 2??K D hQT O CQInventory Management 14 EOQ:Total Cost 0204060801001201401600 500 1000 1500O r d e r Q u a n t i t yCostTotal Cost Order Cost Holding Cost Inventory Management 15 EOQ: Optimal Order Quantity So for our problem (Mug sales), the optimal quantity is 316 2 KDQh? ?* 2 2 0 5 2 1 2Q 3 1 60 . 2 5 1? ? ????Inventory Management 16 EOQ: Important Observations Tradeoff between setup costs and holding costs when determining order quantity. In fact, we order so that these costs are equal per unit time Total Cost is not particularly sensitive to the optimal order quantity Order Qua ntit y 50 % 80 % 90 % 100 % 110 % 120 % 150 % 200 % Co st Increa se 125 % 103 % 101 % 100 % 101 % 102 % 108 % 125 % Inventory Management 17 The Effect of Demand Uncertainty Most panies treat the world as if it were predictable: – Production and inventory planning are based on forecasts of demand made far in advance of the selling season – Companies are aware of demand uncertainty when they create a forecast, but they design their planning process as if the forecast truly represents reality Recent technological advances have increased the level of demand uncertainty: – Short product life cycles – Increasing product variety Inventory Management 18 Demand Forecast The three principles of all forecasting techniques: – Forecasting is always wrong – The longer the forecast horizon the worst is the forecast – Aggregate forecasts are more accurate Inventory Management 19 Swimsuit production Fashion items have short life cycles, high variety of petitors Swimsuit production – New designs are pleted – One production opportunity – Based on past sales, knowledge of the industry, and economic conditions, the marketing department has a probabilistic forecast – The forecast averages about 13,000, but there is a chance that demand will be greater or less than this. Example – Swimsuit production Inventory Management 20 Demand Scenarios D e m a n d Sc e n a ri o s0%5%10%15%20%25%30%800010000 12022 14000 16000 18000Sa l e s Probability Example – Swimsuit production Inventory Management 21 Costs Production cost per unit (C): $80 Selling price per unit (S): $125 Salvage value per unit (V): $20 Fixed production cost (F): $100,000 Q is production quantity Example – Swimsuit production Inventory Management 22 Swimsuit production Scenarios Scenario One: – Suppose you make 10,000 swimsuits and demand ends up being 12,000 swimsuits. – Profit = 125(10,000) 80(10,000) 100,000 = $350,000 Scenario Two: – Suppose you make 10,000 swimsuits and demand ends up being 8,000 swimsuits. – Profit = 125(8,000) 80(10,000) 100,000 + 20(2,000) = $ 140,000 Example – Swimsuit production Inventory Mana