Back in the 60's and 70's it was agreed that the incidence of GII (GID) in western countries was 1:100,000 for MTF. Now, as the medical community has discover that GII is a biological-based medical condition rather than a "life style choice," and since ther is more acceptance in society than before, the estimates are 1:10,000 to 1:30,000 for FMT. The numbers varie fomr country to country. In Singapore for example the rate for FTM iis about 1:3,000. There seems to be 3:1 or 5:1 ratio of MTF to FTM. Interestingly, in Poland the MTF and FMT is 1:1 probably reflecting the genetics of this trait.
Kate