Q: What percentage of the United States population identifies as transgender?

—Al Cooper, Atlanta

A: It's tough to put a number on the percentage of people who identify as transgender in the United States, researchers say.

A 2011 study by the Williams Institute, a think tank at UCLA’s School of Law, placed the percentage at 0.3 percent of adults in the United States.

That study states it reviewed 11 surveys that asked sexual orientation or gender identity questions, but Williams Institute public policy scholar Jody Herman recently told Mother Jones she thinks the number “could potentially be higher than 0.3 percent now.”

Mother Jones is a nonprofit news organization and magazine.

“We can’t really say how many transgender people are in the U.S., and we can’t really say what their demographics look like,” Herman said in the article.

The U.S. Census Bureau doesn’t ask about gender identity in its surveys and census questions, the New York Times reported.

A May 2015 Census Bureau study researched people who had changed their first and/or middle names “from traditionally male to traditionally female names (or vice versa),” it states, or “sex coding” (male to female or vice versa) on their Social Security Administration records, dating to 1936.

It found that “135,367 individuals changed their name or sex-coding in ways that are consistent with a gender transition,” the study states.

Of those, 89,667 were alive during the 2010 Census. And of that group, 21,833 also had changed their sex.

“Learning about the transgender population is difficult, because very few large-scale data sets exist that allow researchers to directly observe whether or not a respondent has transitioned,” the study concluded.

Andy Johnston with Fast Copy News Service wrote this column. Do you have a question? We’ll try to get the answer. Call 404-222-2002 or email q&a@ajc.com (include name, phone and city).