At least 8 million adults in the United States identify as gay, lesbian, or bisexual, according to a new study released Thursday by the Williams Institute.

In total, with approximately 700,000 transgender Americans, nearly 4% of the nation's population is openly LGBT.

Furthermore, an estimated 19 million people, or 8.2%, have engaged in some relationships or sexual behavior with someone of the same sex, and 25.6 million admit to harboring at least some same-sex attraction at some point.

The research shows that slightly more people identify as bisexual (1.8%) than as lesbian or gay (1.7%), and women are more likely than men to identify as bisexual.

The Los Angeles-based think tank came to the number after cross-referencing four recent national and two state-level population-based surveys.

"Last week, the Institute of Medicine at the National Academies released an analysis of LGBT health research calling for federal statistical agencies to quickly move toward LGBT inclusion in their data collection," lead researcher Gary Gates said in a statement. "The surveys highlighted in this report demonstrate the usefulness of sexual orientation and gender identity questions on large-scale national population-based surveys. Better data can provide the building blocks for critical information to understand the lives of the 9 million LGBT Americans who have been historically marginalized in both society and research."