In the early 1900s, Ford Motor ran dozens of tests to discover the optimum work hours for worker productivity. They discovered that the “sweet spot” is 40 hours a week–and that, while adding another 20 hours provides a minor increase in productivity, that increase only lasts for three to four weeks, and then turns negative.

Anyone who’s spent time in a corporate environment knows that what was true of factory workers a hundred years ago is true of office workers today. People who put in a solid 40 hours a week get more done than those who regularly work 60 or more hours.

The workaholics (and their profoundly misguided management) may think they’re accomplishing more than the less fanatical worker, but in every case that I’ve personally observed, the long hours result in work that must be scrapped or redone.