“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.”