At the US automaker where I once worked, assembly plant shifts were scheduled back to back. If one shift finished at 3:00 pm, another was hard at work by 3:30. The plants' managers pushed hard to meet production quotas while minimizing input costs by keeping the line going pretty much all the time. The underlying productivity arithmetic is basic to any manager's: maximize output (cars), minimize inputs (labor, electricity to run the machines, etc.). Interestingly, the world's reigning champ of manufacturing, Toyota, doesn't follow this logic.