Demand and Uncertainty

Almost every monthly meeting I had with a large consumer of capacity carried a seasonal question. In the spring it was “How much can we save?” In the fall it was “Are we really ready? Are we prepared?” Most businesses run on that yearly cadence, and both questions are about the forecast. Underneath both is the question Volume I, Chapter 2 put at the center of capacity: how do we make good commitments when we can’t know what we’re going to need?

Someone usually knows that next month’s demand will differ from the historical pattern. We should talk to that person, but we should also keep the original forecast: their information might improve the decision, or the plan might change again and leave our adjustment looking worse than the baseline. I want a forecasting practice that can learn from either result.

This part puts the mathematics and the conversations together, retaining what we knew at the time so that hindsight doesn’t quietly improve our record. We then widen the view from one workload to the large consumers, the long tail, and the shared changes that can affect both. At that level, getting to a total is only part of the work. We have to understand which customer promises and supply constraints disappear when we add everything up.