Employees assemble vehicle chassis modules on a production line at the Hyundai Mobis Co. factory in Asan, South Chungcheong, South Korea. (SeongJoon Cho/Bloomberg)

South Korea's parliament is putting a lid on what an official there has called its "inhumanely long" work hours, passing a bill that would cut the maximum workweek from 68 hours down to 52. In doing so, it is setting the limit right around where research has shown that health conditions start worsening and productivity starts falling off.

South Koreans worked an average 2,069 hours in 2016, more than any country in the Organization for Economic and Cooperative Development other than Mexico and Costa Rica. The new bill would limit weekly hours to the regular 40 hours per week and permit up to 12 hours of overtime and include weekend hours in that tally, paid at an overtime rate of 50 to 100 percent additional pay, according to Bloomberg.

The cuts fulfill a campaign promise by President Moon Jae-in, elected last year, and are aimed at improving quality of life, creating more jobs and boosting the country's declining birth rate, according to media reports. Family minister Chung Hyun Back told the AFP in January that "for years, we have overlooked the real culprit of the problem - our country's vast gender disparity and inhumanely long working hours."

But the limit is also aimed at boosting productivity, and as a result, the upper limit figure seems to be a wise choice -- or close to it. Research published in 2014 by an economist at Stanford University showed that after about 50 hours, productivity started to fall off. After 55 hours, it fell precipitously, with little difference in output from 56 to 70 hours. (The study looked at data about munitions workers from a British factory during World War I, when the workweek often stretched between 60 and 100 hours.)

As an article in the Economist from that year put it: "That extra 14 hours was a waste of time." And while the study obviously didn't address jobs in today's service economy, the effect could be even stronger. "For work that is largely self-directed, and which requires intellectual engagement, you may achieve more in an hour of hard work than in a day's worth of procrastination," the Economist surmised.

Other research shows health benefits of keeping weekly hours below 55 hours. One study in the Lancet found that working more than that 55-hour threshold was associated with a higher risk of developing Type 2 diabetes. Previous research has associated working more than 11 hours a day with higher heart attack risks, and yet another study linked working more than 55 hours a week with more disturbances in workers' sleep.

Whether that magic 55-hour mark is simply a number chosen by researchers -- as some told OnLeadership in 2015 -- or an actual threshold above which continuing to work has little payoff, it's clear that myriad consequences seem to follow from working too many hours. Not only can productivity fall, health problems increase, and quality of life go down, but it can create gender disparities, limit women's opportunities in the workplace (especially in more traditional cultures) and even apparently impact a country's birth rate.

South Koreans may be getting a cap on its weekly hours, but what about Americans? Many U.S. workers, of course, are not covered by overtime protections. But among those who are, employment lawyers say that other than in certain job categories (airline pilots, for instance, or interstate truckers), federal law does not set a maximum number of overtime that employees may work.

Some state regulations do require having one day's rest in seven, or a number of hours off between shifts. But "as far as I know, no state or locality has specified a maximum number of hours that an employer may ask an employee to work as a matter of generally applicable law," said Paul DeCamp, a former administrator of the Department of Labor's Wage and Hour Division and now an attorney with Epstein Becker Green in Washington.

For now at least, workers in the United States actually work a good bit less than some other OECD countries. The annual average in 2016 in the country was 1,783 hours -- about 100 hours less than workers in Iceland, Israel and Lithuania, and nearly 300 less than in South Korea.

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