Don’t keep adding to your weekly hours: past about 49 hours, each extra hour yields less and less
Grade BBig benefitTimeLow costLittle timeSome willpower
Records from British munitions factories during World War I show that when workers kept weekly hours under 49, output rose in direct proportion to the time spent working. Once they exceeded 49 hours, the growth rate began to drop. Output from workers putting in 70 hours per week was practically identical to that of those working 56 hours — those extra 14 hours yielded no additional results. In total, this data covers a period spanning 100 years.
- Cost
- You might earn less in overtime pay. You may also need to put in effort to negotiate with your supervisor.
- Benefit
- Data from British munitions factories in World War I demonstrates that output rises steadily with working hours up to 49 per week. After that threshold, the rate of growth slows. Peak output is reached at roughly 63 hours. At 70 hours, output remains essentially the same as at 56 hours, meaning those extra 14 hours are wasted effort.
- Notes
- These figures come from factories a century ago where most workers were women performing manual labor. This threshold may differ for cognitive work; the authors themselves note that other occupations could have higher or lower limits. What is reliable, though, is the overall trend: beyond a certain point, adding more hours yields almost no extra output. The specific figure of 49 hours is not proven.
Sources · 1
- Pencavel (2015). The Productivity of Working Hours. The Economic Journal. doi.org/10.1111/ecoj.12166