One of the things YC could do to help with their horrible 4% ratio is get Hacker News to be less hostile to women. Quite a few women founders have told me how unpleasant they find it here. This thread is a good example of why.
It's funny, I see comments like yours in most related threads, and I don't agree.
There's enough of a sensible audience here to downvote hostile replies, and - far more importantly - to upvote the supportive ones. Guess which type of reply is likely to receive more respect and attention, particularly among female readers?
So I would venture to say that the '4% ratio' is due to something else, and we'd be far better off not hiding behind false/stereotyped/politically-correct make-believe.