Analysis of this data for 2015 showed that performance increased with increasing working time, but only up to a point. The performance per hour reached a peak of about 40 hours of work per week and then went down.
The study author Dr. Stanford University economics professor John H. Pencavel states that the number of hours worked per week is a big problem. "After one point (a point that is likely to vary between workers and their jobs), another hour of work will provide more power (or better performance) if the employee has already worked 30 hours a week than if the employee has already worked 40 hours a week, "he says by e-mail.
Pencavel discusses the same munitions workers in his book Reducing Labor Return: The Consequences of Long Working Hours. There he explains that the workers usually worked more than 50 hours a week and sometimes even up to 72 hours. Pencavel's figures show that the weeks in which production was highest were not the same weeks when the hours were the longest. [1
Occasionally ammunitionettes had to take a Sunday off, however. The HMWC collected data on both conditions and found that a work week without a rest day is of no use to anyone. Production is not rising and the workers are unhappy.