leveling effect. The graphs on the left illustrate the variation in customer demands for individual parts needed to support production operations. Managing them individually requires some sort of buffering, either padding production schedules or accumulating inventories, to ensure their timely delivery despite severe uncertainty in demand. Yet these buffers represent sources of lag that respond poorly to changing circumstances. As described in Chapter 2, despite working well within a stable environment, these actions might break down and make matters even worse when conditions suddenly shift.