Only 0.3 percent of the United States population is comprised of trans people, or roughly 700,000 individuals, per the Williams Institute.
The Williams Institute came to their estimate by averaging the findings from two sets of survey data, one from California and one from Massachusetts; they published their results in 2011.
As described by The New York Times, “One was a statewide health survey in Massachusetts that asked people if they were transgender and found that 0.5 percent of people said they were. Another was a California survey about tobacco use among lesbian, gay, bisexual and transgender people. Just over 3 percent identified as transgender, implying that 0.1 percent of adults in California were transgender, based on the Williams Institute’s estimate of the percentage of the total population that is L.G.B.T.”
Further, as noted by The Daily Caller, a similar study from the United Kingdom "found that only 0.1 percent of the UK population was transgender." This study focused on only those individuals who actually underwent a sex change, as opposed the surveys by the Williams Institute, which focused on those who merely identified as trans.
This is undeniably a stunningly small percentage of Americans, especially considering the Left’s recent mass trans-hysteria; from the substantial backlash against North Carolina for overturning a trans ordinance via House Bill 2 to President Obama’s overreaching federal edict requiring all public schools to open locker-room and bathrooms to “gender identity” at the threat of lawsuits and revoked funding.
Many on the Left refute the findings, suggesting that the population is larger, since, for one reason or another, (a possible fear of backlash), trans individuals might not have answered the survey honestly. Contrarily, some on the Right point to evidence which might have actually inflated the total estimation. Per The Daily Caller:
0.3 percent might actually be too high of a number. The Williams Institute’s researchers arrived at the commonly-cited 0.3 percent figure by averaging the results of two studies — one in Massachusetts and one in California.
The Massachusetts study found that 0.5 percent of the population was transgender, while the California study found that transgenders made up just 0.1 percent of the population. That is: the California study found only one in 1000 Californians to be transgender.
Either way, the trans population is incredibly tiny. And this is not to say that they have been slighted by so-called anti-LGBT legislation, either. For example, House Bill 2 (AKA the “bathroom bill”) accommodates trans individuals who have undergone a sex change. The law explicitly states that individuals must use the locker-room or restroom that coordinates with their stated gender on their birth certificate—which can be changed post-op. Further, trans individuals have and can be accommodated by the other 99.7 percent of the population. Changing the state of federal laws to switch that seems nonsensical, or in the least, impractical.