The Effect of Vendor Managed Inventory (VMI) Dynamics on the Bullwhip Effect in Supply Chains

The paper compares the expected performance of a Vendor Managed Inventory (VMI) supply chain with a traditional “serially-linked” supply chain. The emphasis of this investigation is the impact these two alternative structures have on the “Bullwhip Effect” generated in the supply chain. We pay particular attention to the manufacturer’s production ordering activities via a simulation model based on difference equations. VMI is thereby shown to be significantly better at responding to volatile changes in demand such as those due to discounted ordering or price variations. Inventory recovery as measured by the Integral of Time * Absolute Error (ITAE) performance metric is also substantially improved via VMI. Noise bandwidth, that is a measure of capacity requirements, is then used to estimate the order rate variance in response to random customer demand. Finally, the paper simulates the VMI and traditional supply chain response to a representative retail sales pattern. The results are in accordance with “rich picture” performance predictions made from deterministic inputs.