This fact should be drilled into the heads of managers everywhere - Henry Ford, one of America's great entrepreneurs and businessmen, set his workers' shifts to

This fact should be drilled into the heads of managers everywhere - Henry Ford, one of America's great entrepreneurs and businessmen, set his workers' shifts to 8 hours not out of some love or sympathy, but because 8 hours is the maximum work you can extract from a human being in a day. It's not some average or medium amount, it's the maximum sustained amount. If they could do 9, he would have had them do 9.