Personally, I am not sure that Maths actually works in matters that are deep rooted feeling within people, as people are very good at keeping things hidden unless they can't or can no longer control... for example... Me!
I was dysphoric since a very young kid, did not understand, certainly no labels... Hid and denied it for many years, but guess what I can't control the feelings anymore... I did not need diagnosis, I do not therefore appear on any reports. However I have in last 10 ~ 12 years been getting HRT from a Dr, have I been defined in the reports? very unlikely!
I think with transgender, most that fall into this group will all have different requirements, drivers and needs, some enjoy cross dressing, others just enjoy saying that they are and are convincing enough, others as Jill has mentioned do not appear on the radar until they try and harm themselves... For me HRT was a requirement to get me to a point where, at my age, I can at least make an attempt to fully transition, for me I would not have been able to move in that direction without, I would not mind betting that there are many others like me... Of course once I go for name change etc. and fully recognised as transgender, and on HRT, then I will become a statistic.
Either way (IMHO) statistics are not representative of a state of affairs, unless it captures all aspects of the subject matter, and can be retrospective, as there in itself shows an even larger diversification... With forums there are some who can live their dreams without actually stepping over any line... Which I must admit I did some 12~15 years ago... however for me that was the realization that I can actually do something about the feelings. Eureka!

Of course this is just my views and ramblings
L Katy