Nearly half of U.S. workers say they routinely put in more than 50 hours on the job each week, often without overtime pay. But employers should probably start politely declining the "free" gift, new research suggests.

So-called "work martyrs" give hundreds of hours in free labor to their employers every year, encouraged by always-on gadgets, work through nights, weekends, and vacations. Trading sleep or fun for unpaid work is obviously a bad deal for employees, but there's a growing body of evidence that even apparently "free" labor might not be a good deal for employers, either.



Research that attempts to quantify the relationship between hours worked and productivity found that employee output falls sharply after a 50-hour work-week, and falls off a cliff after 55 hours—so much so that someone who puts in 70 hours produces nothing more with those extra 15 hours, according to a study published last year by John Pencavel of Stanford University. Longer hours have also been connected to absenteeism and employee turnover. The Centers for Disease Control and Prevention even has an entire website devoted to the effects of long working hours even if workers aren't paid for this extra time. It's not free, Pencavel points out.

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"There are ancillary costs of long working hours such as the expenses of running complementary machinery and of providing light, heat, ventilation, and supervisory labor," he said in the study.



The idea that work hours can be cut without a drop in productivity should be good news for both American workers and their bosses, who routinely put in more hours than seem productive. In a Gallup poll last year, 4 in 10 Americans said they work more than 50 hours every week, and 2 in 10 more than 60 hours. The average work week was 47 hours.



Despite the research, don't expect Americans to be better about getting home for dinner any time soon. Not only are hours worked per week on the rise, but technology seems to be irresistibly driving the trend. A recent Pew survey found that 35 percent of adults say the Internet, email and cellphones have increased their hours worked. For office workers, the number rises to 47 percent.



Also contributing to this nonvirtuous cycle of overwork: Employees are trading sleep for work. Researchers at the University of Pennsylvania Perelman School of Medicine examined detailed time-use studies and found that people who said they slept six hours or less at night worked 1.5 hours more than others who got more sleep.