Gary J. Gates, Williams Distinguished Scholar at the UCLA School of Law, said he compiled his information from four recent national and two state-level population-based surveys.
Gates published his findings this month under the title "How many people are lesbian, gay, bisexual, and transgender?"
His research indicates about 3.5 percent of the U.S. population is LGBT. About 700,000 adult Americans fall into the transgender category.
"Understanding the size of the lesbian, gay, bisexual, and transgender (LGBT) population is a critical first step to informing a host of public policy and research topics," Gates' report said. "Examples include assessing health and economic disparities in the LGBT community, understanding the prevalence of anti-LGBT discrimination, and considering the economic impact of marriage equality or the provision of domestic partnership benefits to same-sex couples."
Among the findings: women are more likely than men to identify as bisexual; about 19 million respondents say they have engaged in same-sex sexual behavior; nearly 26 million Americans -- 11 percent -- acknowledge some same-sex sexual attraction.
The entire report can be read at: http://www2.law.ucla.edu/williamsinstitute/pdf/How-many-people-are-LGBT-Final.pdf.