SAN FRANCISCO (AP) - How many gay men and lesbians are there in the United States? Gary Gates has an idea but acknowledges pinpointing a solid figure remains an elusive task.
Gates is demographer-in-residence at the Williams Institute on Sexual Orientation Law and Public Policy, a think tank based at the University of California, Los Angeles. For the institute's 10th anniversary this week, he took a scholarly stab at answering the question that has been debated, avoided, parsed and proven both insoluble and political since pioneering sex researcher Alfred Kinsey said in the 1940s that 10 percent of the men he surveyed were "predominantly homosexual."
Gates' best estimate, derived from five studies that have asked subjects about their sexual orientation, is that the nation has about 4 million adults who identify as being gay or lesbian, representing 1.7 percent of the 18-and-over population.
That's a much lower figure than the 3 to 5 percent that has been the conventional wisdom in the last two decades, based on other isolated studies and attempts to discredit Kinsey.
One reason, according to Gates, is that until recently, few surveys tried to differentiate respondents who identified as gay or lesbian from those who sometimes engaged in homosexual acts or were attracted to people of the same sex. All were lumped into the gay category.
"One of the major questions, when you think about how many (lesbian, gay, bisexual and transgender) people are there, is what do you mean by LGBT?" he said. "This shows there are pretty big differences between people who use the terms to label themselves versus sexual behavior or attraction."
Gates found, for example, that another 1.8 percent of the adult population, or a little more than 4 million Americans, identifies as bisexual, according to his research brief published Thursday by the Williams Institute.
He also estimated that 19 million people, or 8.2 percent of the population, have engaged in sex with a partner of the same sex. That includes all groups, such as gays, bisexuals and heterosexuals who have experimented with same-sex behavior.
Another two studies, conducted by state agencies in California and Massachusetts, yielded what Gates thinks is the first credible estimate of the nation's transgender population. He puts it at about 700,000 adults, or 0.3 percent of the population.
Gates is the first to admit his figures are imprecise.
But because so few national population surveys have asked about sexual orientation and the ones that have were not conducted consistently over time, the data on which to base a firm conclusion does not exist, he said.
"Yes, this is a credible estimate, but I'm fine to have a debate with someone about whether I'm right or wrong," he said. "The academic side of me says everything comes with caveats. But there is a level of power associated with having a number that can move dialogues along and hopefully move things forward."
Government agencies and private researchers have been reluctant in the past to include questions about sexual orientation and gender identity in their surveys, deciding the issue was not worthy of inquiry or assuming participants would be reluctant to answer honestly.
Until recently, gay rights activists who feared that it would be used to discriminate against or to identify individuals, during the AIDS crisis, for example, also opposed divulging such information.
Brad Sears, the Williams Institute's executive director, recalled Gates' 2006 estimate, which was drawn from Census data on same-sex households and put the nation's lesbian, gay and bisexual population at about 8.8 million. That news upset some gay people who found comfort in Kinsey's 1-in-10 number, Sears said.
"There are a lot of great folks for whom that number may have personally been important in their coming-out process," Sears said. "It may be hard to let go. But with other populations of a similar size of 2 to 4 percent, we don't question whether there are too many or too few."
Some advocates say they will still keep fighting for equality, regardless of the numbers.
Winnie Stachelberg, a senior vice president at the Center for American Progress who specializes in gay and lesbian issues, said advocates will keep arguing on behalf of gay-rights issues, including the military's recently overturned ban on openly gay troops, because quality - not quantity - is what ultimately drives them.
"Repealing 'don't ask, don't tell' was in the interest of national security and the integrity of those serving - not about the actual numbers serving," said Stachelberg, who worked with Gates previously on a Census study of gay families.
Peter Sprigg, senior fellow for policy studies with the conservative Family Research Council, welcomed Gates' findings as further repudiation of the Kinsey 1-in-10 estimate.
Sprigg also was intrigued by the relatively high portion of bisexual people tallied by Gates.
"I see this as somewhat of a problem for the gay political movement," Sprigg said. "It undermines the idea that being born homosexual is an immutable characteristic that can't be changed."
Increasingly, both activists and the federal government during the Obama administration have concluded that the advantages of having reliable information about sexual minorities far outweighed any risks.
Last year, Gates advised the Census bureau in its campaign to persuade same-sex couples to identify themselves as such in the once-a-decade national population count. The bureau is now considering whether to ask individuals about their sexual orientations in the ongoing American Community Survey produced in between each Census.
The U.S. Department of Health and Human Services last week announced it was working to increase the number of federally funded health and demographic surveys that collect and report sexual orientation and gender identity data.