> But entrepreneurs are mostly healthy young men

Could this be at least in part a self-fulfilling prophecy? Due to the way healthcare is set up in the U.S., the only people who really can consider quitting their jobs, and losing their group-health plan as a result, are: 1) people who are already rich (or have rich family); and 2) healthy young men.

edit: Actually, I suppose people over 65 also can, due to the U.S.'s strange age-based national health system. But people over 65 tend not to be likely startup candidates for other reasons.