Transgender
One effort to quantify the population gave a "rough estimate" that 0.3 percent of adults in the US are transgender, overlapping to an unknown degree with the estimated 3.5 percent of US adults (1-in-30) who identify as LGBT. More recent studies released in 2016 estimate the proportion of Americans who identify as transgender at 0.5 to 0.6%. This would put the total number of transgender Americans at approximately 1.4 million adults ().
Transsexual
Olyslager and Conway presented a paper at the WPATH 20th International Symposium (2007) arguing that the data from their own and other studies actually imply much higher prevalence, with minimum lower bounds of 1:4,500 male-to-female transsexual people and 1:8,000 female-to-male transsexual people for a number of countries worldwide. They estimate the number of post-op women in the US to be 32,000 and obtain a figure of 1:2500 male-to-female transsexual people. They further compare the annual incidences of sex reassignment surgery (SRS) and male birth in the U.S. to obtain a figure of 1:1000 MTF transsexual people and suggest a prevalence of 1:500 extrapolated from the rising rates of SRS in the US and a "common sense" estimate of the number of undiagnosed transsexual people. Olyslager and Conway also argue that the US population of assigned males having already undergone reassignment surgery by the top three US SRS surgeons alone is enough to account for the entire transsexual population implied by the 1:10,000 prevalence number, yet this excludes all other US SRS surgeons, surgeons in countries such as Thailand, Canada, and others, and the high proportion of transsexual people who have not yet sought treatment, suggesting that a prevalence of 1:10,000 is too low.