Sara Robinson writes:
In 1937, the 40-hour week was enshrined nationwide as part of the New Deal. By that point, there were a solid five decades of industrial research that proved, beyond a doubt, that if you wanted to keep your workers bright, healthy, productive, safe and efficient over a sustained stretch of time, you kept them to no more than 40 hours a week and eight hours a day.... increasing a team’s hours in the office by 50 percent (from 40 to 60 hours) does not result in 50 percent more output (as Henry Ford could have told them). Most modern-day managers assume there will be a direct one-to-one correlation between extra hours and extra output, but they’re almost always wrong about this.If you’re a knowledge worker, the truth of this may become clear if you think about your own typical work day. Odds are good that you probably turn out five or six good, productive hours of hard mental work; and then spend the other two or three hours on the job in meetings, answering e-mail, making phone calls and so on. You can stay longer if your boss asks; but after six hours, all he’s really got left is a butt in a chair. Your brain has already clocked out and gone home.