Well it depends if you are talking TS or crossdressing, not the same thing, not the same numbers. I think this topic has been raised her at least once or twice.
Depending on which research (and conclusion) you ascribe to, there are many different theories. I tend to believe that, first off, males displaying feminine characteristics are more discouraged than the converse. This lack of acceptance can do a couple of things. Lead to repression, or act as a neutral zone barrier. No one cares if a girl is a tomboy, in fact it is often rewarded. But the other way is not. Maybe those feminine characteristics remain hidden until they overwhelm the individual and they jump the barrier. Kind of like electron hole theory.
Girls can be kind of, guy is or aint. Maybe. Plus it's a woman's prerogative to change her mind. Guys are stuck with their stupid decisions
