As demonstrated in another thread - unless we are talking about people who would've previously been described as "transsexual" - ie they want to be the opposite sex - there isn't really a consensus on how to define who is or isn't "trans" under the wide and nebulous umbrella, so that would need to be clarified before it could be measured.
If people (adults) want to be the opposite sex and take steps to be treated like they are, I have no issue with that in most situations. Taking a driving test, going to the pub, decorating a room, walking down the street, doesn't matter to me if they're a man or a woman.
It's the few where biological sex matters that we need to ensure we're not conflating sex and gender.