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The Bullwhip Effect in Supply Chains
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By Hau L. Lee, V. Padmanabhan and Seungjin Whang
Spring 1997
Reprint 3837
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Volume 38, Number 3, pages 93-102, 10 pages
Primary Topic: Operations
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SummaryTremendous variability in orders along the supply chain can plague companies trying to eliminate excess inventory, forecast product demand, and simply make their supply chain more efficient. What causes the bullwhip effect that distorts information as it is transmitted up the chain? The authors identify four major causes: 1. Demand forecast updating. As each entity along the chain places an order, it replenishes stock and includes some safety stock. With long lead times, there may be weeks of safety stocks, which make the fluctuation in demand more significant. 2. Order batching. Companies may place orders in batches, often to avoid the cost of processing orders more frequently or the high transportation costs for less-than-truckload orders. Suppliers, in turn, face erratic streams of orders, and the bullwhip effect occurs. When order cycles overlap, the effect is even more pronounced. 3. Price fluctuation. Special promotions and price discounts result in customers buying in large quantities and stocking up. When prices return to normal, customers stop buying. As a result, their buying pattern does not reflect their consumption pattern. 4. Rationing and shortage gaming. If product demand exceeds supply, a manufacturer may ration its products. Customers, in turn, may exaggerate their orders to counteract the rationing. Eventually, orders will disappear and cancellations pour in, making it impossible for the manufacturer to determine the real demand for its product. The authors suggest several ways in which companies can counteract the bullwhip effect: 1. Avoid multiple demand forecast updates. Companies can make demand data from downstream available upstream. Or they can bypass the downstream site by selling directly to the consumer. Also, they can improve operational efficiency to reduce highly variable demand and long resupply lead times. 2. Break order batches. Companies can use electronic data interchange to reduce the cost of placing orders and place orders more frequently. And they can ship assortments of products in a truckload to counter high transportation costs or use third-party logistics companies to handle shipping. 3. Stabilize prices. Manufacturers can reduce the frequency and level of wholesale price discounting to prevent customers from stockpiling. They can also use activity-based costing systems so they can recognize when companies are buying in bulk. 4. Eliminate gaming in shortage situations. In shortages, suppliers can allocate product based on past sales records, rather than on orders, so customers don't exaggerate their orders. They can also eliminate their generous return policies, so retailers are less likely to cancel orders. Only by thoroughly understanding the underlying causes of the bullwhip effect, say the authors, can companies counteract and control it. |
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