The research says 85% of American girls were under 17 when they were first harassed, but like you, I've never met a woman who didn't have that start for them at 10, 11 or 12. And, as you noted, it wouldn't be so common if it weren't tolerated as "just how things are." To me, it's one of the clearest examples of how rape culture is fostered and supported by normalizing and turning a blind eye to reprehensible behavior.