This is one case where the raw numbers tell more of a story than the percentages. Distance running as a whole is healthier with, say, one 2:50 guy and one 3:05 guy than one 2:50 guy. But in the former case, only 50% of runners, not 100, will have broken 3 hours.
Especially when considering that women have started running marathons.
That said, I'm pretty sure that the raw numbers would show the same thing.