Destocking, the bullwhip effect, and the credit crisis: Empirical modeling of supply chain dynamics

In this paper we analyze the strong sales dip observed in the manufacturing industry at the end of 2008, following the bankruptcy of Lehman Brothers and the subsequent collapse of the financial world. We suggest that firms׳ desire to retain liquidity during these times prompted a reaction characterized by the reduction of working capital, which materialized as a synchronized reduction in target inventory levels across industries. We hypothesize that such a reaction effectively acted as an endogenous shock to supply chains, ultimately resulting in the bullwhip-effect kind of demand dynamics observed. To test this proposition we develop a system dynamics model that explicitly takes into account structural, operational, and behavioral parameters of supply chains aggregated at an echelon level. We calibrate the model for use in 4 different business units of a major chemical company in the Netherlands, all situated 4-5 levels upstream from consumer demands in their respective supply chains. We show that the model gives a very good historical fit of the sales developments during the period following the Lehman collapse. We test the model׳s robustness to behavioral parameter estimation errors through sensitivity analysis, and the de-stocking hypothesis against an alternative model. Finally, we observe that the empirical data is aligned with experimental observations regarding human behavioral mechanisms concerning target adjustment times.