It is widely known that lead-time and utilization are dependent on work in progress (WIP). This article validates the
functional relationship between inventory deviation and lead-time by means of simulation. In addition, the results
con¯rm a new mathematical model for the logistic operating curves in practice. A new approach is based on the idea
that changing a machine from overload to underload and vice versa results in a waste of utilization and therefore in
an increase in lead-times. The frequency of the changes from under- to overload and vice versa which determines this
waste, is measurable by means of the statistical deviation of the inventory.