> Most manufacturing jobs is done on a conveyor belt. More time is more stuff. The 40 hour work week actually comes to us from research on the original assembl

> Most manufacturing jobs is done on a conveyor belt. More time is more stuff. The 40 hour work week actually comes to us from research on the original assembly line. Henry Ford's analysts apparently concluded that 40 hours was optimal for overall productivity. Past that point and the cost due to the greater number of human errors more than canceled out the additional work. I would wager that this optimal number is different for different people but also for different professions. In professions where fatigue doesn't result in more mistakes or mistakes are cheaper to rectify then the "optimally productive" hours per week might be higher. In professions where fatigue results in even more mistakes and mistakes are more expensive to rectify then the reverse might be true. And this says nothing of the leverage of the workers themselves -- I suspect software engineers can get away with working fewer hours if they want to due to the fact that they have more leverage than most workers.