Putting it precisely, activating a resource and utilizing a resource are not synonymous. - Eliyahu M. Goldratt

[Operating expense is defined as] all the money the system spends in turning inventory into throughput.

Somewhere in the scientific method lies the answer for the needed management techniques. It is obvious.

Flow means that inventories in the operation are moving. When inventory is not moving, inventory accumulates. Accumulation of inventory takes up space. Therefore, an intuitive way to achieve better flow is to limit the space allowed for inventory to accumulate. To achieve better flow, Ford limited the space allotted for work-in-process between each two work centers.