Americans work longer hours and take fewer vacations than most others in the developed world.
We shoot each other more often as well.
With the possible exception of Postal workers (sorry, stereotyping) people who work 60-hour weeks and take no vacations are unlikely to be the ones doing the shooting -- they are doing the work of two people, and that other guy, the guy whose job the over-achiever has eliminated, is more likely to one with time to spare to go out murdering.
As productivity increases, companies can get more done with fewer workers. Good for profit margins, not so good for unemployment rates.