The bullwhip effect
is a distribution channel phenomenon in which forecasts yield supply chain
inefficiencies. It refers to increasing swings in inventory in response to shifts in customer demand as one moves further up the supply chain. The concept first appeared in Jay Forrester's Industrial Dynamics
(1961) and thus it is also known as the Forrester effect
. The bullwhip effect was named for the way the amplitude
of a whip increases down its length. The further from the originating signal, the greater the distortion of the wave pattern. In a similar manner, forecast accuracy
decreases as one moves upstream along the supply chain. For example, many consumer goods
consistent consumption at retail. But this signal becomes more chaotic and unpredictable as you move away from consumer purchasing behavior.
In the 1990s, Hau Lee, a Professor of Engineering and Management Science at Stanford University, helped incorporate
the concept into supply chain vernacular using a story about Volvo. Suffering a glut
in green cars, sales and marketing developed a program to move the excess inventory. While successful in generating the desired market pull, manufacturing did not know about the promotional plans. Instead, they read the increase in sales as an indication of growing demand for green cars and ramped up production.
Research indicates a fluctuation in point-of-sale demand of +/- five percent will be interpreted by supply chain participants as a change in demand
of up to +/- forty
percent. Much like cracking a whip, a small flick of the wrist (a shift in point of sale demand) can cause a large motion at the end of the whip (manufacturer