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You really can work longer hours without killing your productivity

Time to go home.
By Sonali Kohli
Published Last updated This article is more than 2 years old.

So you think you’ve got it bad?

According to a paper by Stanford economics professor John Pencavel, which the Economic Journal published online, back in World War I, the working week stretched anywhere from 60 to 100 hours, to meet the demand for war-related materials. (Here is a pdf of a longer version of the report published earlier this year, via the Economist)

Even in 1916, the British government found the work hours excessive. According to a report that Pencavel dug up from the British Health of Munition Workers Committee, tasked with figuring out how to increase efficiency in munitions plants, the committee recommended making some changes. It proposed giving a rest day on Sundays, and reducing working hours to 65-67 a week for men and boys, and to 60 hours a week for girls and women (who by the end of the war accounted for 77.6% of ammunition and explosives industry employees).

The committee claimed that total output would be unchanged, even with shortened hours. Pencavel was curious to test that hypothesis, applying statistical analysis techniques to the data the committee had gathered for their report. Here’s what he found:

[B]elow 49 weekly hours, variations in output are proportional to variations in hours; for those observations corresponding to 49 or more hours, output rises with hours at a decreasing rate and a maximum of output occurs at about 63 hours. Output at 70 hours differs little from output at 56 hours

So employees increased in productivity up to 49 hours. After that, they were productive, but at a slower pace, up to 63 hours. And then productivity dropped off. Pencavel also found that employees who took Sunday off were better off.

“What was particularly damaging was the absence of a day of rest,” Pencavel tells Quartz. “In fact, working six days for eight hours a day would have produced slightly more output than working 70 hours over a seven-day work week.”

Obviously, these data are limited in their scope—they measure how many pieces of shells or other war material a World War I factory employee produced under working conditions very different from today’s workers, and Pencavel says he is working on analyzing more contemporary data. But they do offer a clear correlation between output and working hours.

That working less than the standard 40-hour week does not make you more productive is not a message that fans of a three day week or a six hour work day or just working part time forever are going to be thrilled to hear. But for the modest workaholics among us, go ahead, work 50 hours a week if you must. Just take a break every once in a while.

📬 Kick off each morning with coffee and the Daily Brief (BYO coffee).

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