The recent debate over public restroom access for transgender people has prompted some questions on just how big an issue this is — how many people are affected by such rules? The size of the transgender population is tricky to estimate, for reasons we discussed almost a year ago, in the article below:

When Caitlyn Jenner, formerly known as Bruce Jenner, unveiled her new name, appearance and TV show last week, it shined a light on transgender Americans. But much about the community, such as its size, remains opaque.

The main reason is that the United States Census Bureau and other keepers of official records do not ask about gender identity. Also, gender identity can be fluid and hard to define in a multiple-choice list. There are now more than 50 gender options on Facebook, for instance.

Some researchers are also concerned that the number is undercounted because of a reluctance among some transgender people to discuss it with survey takers or signify it on a government form. In a study by the National Center for Transgender Equality and the National Gay and Lesbian Task Force, 71 percent of transgender people said they hid their gender or gender transition to try to avoid discrimination.

Yet knowing more about transgender people is important for policy-making in health, education, criminal justice, social services, sports, the military and more.