Comment by marcosdumay

Proportional-only buffer management makes the bullwhip effect worse.

You need an integral part that knows what the entire chain reaction time is. But if you don't have a buffer, you can't do that part, you can only react strictly to the conditions your suppliers have right now.

A derivative part seems quite useless in a non-coordinated game. But it could in theory pass a "message" upchain that they need to start reacting. Anyway in any real situation it will be easier to pass a message around by telling stuff to people.

At the end of the day, the relative penalty for storage or non-delivery is what will dictate the optimum play style. But it's perfectly viable to use buffers to attenuate the bullwhip instead of making it larger.