How human behaviour amplifies the bullwhip effect. A study based on the beer distribution game online

The bullwhip effect is one of the main reasons for inefficiencies in supply chains. Since Forrester discovered around 45 years ago that variations of demand (and based on that of orders and stocks) increase up the supply chain from customer to supplier [1], researchers look for reasons and try to find countermeasures. Nevertheless the role that human behaviour plays in the bullwhip effect is still overlooked. This article will -- after a literature survey of classical reasons for the bullwhip effect, that have been found so far -- describe the beer distribution game online, which is a web-based simulation of a supply chain with four comakers. Results of this simulation (with so far more than 400 people taking part) allow for the first time to analyse, how humans perform as a co-maker in a supply chain compared to simple agent-based strategies. The analysis shows, that aspects in human behaviour have to be added to the list of reasons for the bullwhip effect.