WASHINGTON -- A few salient facts are known about the Americans whose lives might be changed by a Supreme Court ruling on same-sex marriage expected this summer.
About 1 in 5 gay and lesbian couples are raising children under age 18. Same-sex couples are less likely than traditional married couples to have health insurance covering them both. One in 10 men with a male partner or spouse is a military veteran. As many as 6 million Americans, roughly 2 percent of the population, have a parent who is lesbian, gay, bisexual or transgender.
These nuggets of demographic insight into same-sex couples were contained in an amicus brief filed last week in connection with two cases before the Supreme Court on the constitutionality of California's gay marriage ban and the federal Defense of Marriage Act. Although posed in dry, academic language, the statistics represent a remarkable step forward in what is known about the lives of lesbians and gays.
As gays become more visible in politics, challenging laws that stigmatize their relationships, demographic research into lesbians and gays is emerging from the shadows. Some gay advocates say it's time for surveys to ask people point-blank to identify their sexual orientation.
"There is quite a bit about the LGBT population we don't know," said Gary Gates, the most prominent of only a few demographers focusing on gay statistics, who drew on census data for the demographic brief filed in the Supreme Court. "As a political and cultural issue, it's very important for us to understand how big and visible this population is."
Gay activists say they need even more research done, sometimes just to make the case that they exist in every community.
"When our legislative affairs director goes into congressmen's offices, they're often told, 'I have no gay people in my district,' " said Fred Sainz, a spokesman for the Human Rights Campaign, a civil rights group urging protections for gays. "That's why this demographic information is so incredibly important. Gay and lesbian couples live everywhere across the country. We are not some kind of unique species."
Yet gay activists have been some of the most vocal critics of Mr. Gates, the demographer, who is affiliated with the UCLA School of Law's Williams Institute, which studies sexual orientation and gender identity. They say his research, showing 3.8 percent of Americans are LGBT and fully half of those identify themselves as bisexual, underestimates their numbers and marginalizes their concerns.
Some controversy is rooted in a late-1940s study by Sexologist Alfred Kinsey that included a passing reference that 10 percent of men had had same-sex experiences. That figure has stuck, in part, Mr. Gates says, because gay activists cited it to make the case that they could not be ignored.
Some gay marriage foes say more research should be done in part to correct popular misperceptions on the gay community's size. In several surveys, Gallup has found that Americans believe, on average, that 25 percent of the population is gay. "I think serious data on this is important to inform the debate," said Peter Sprigg, a senior fellow at the Family Research Council, which has argued that same-sex marriage harms society. "People have an exaggerated view of how many homosexuals there are in the population."
The 2010 census counted 646,000 couples living with same-sex partners, including 130,000 same-sex married couples. The National Gay and Lesbian Task Force, which waged a campaign urging same-sex couples to identify themselves on the federal questionnaire, wants the census and other government surveys to ask more questions about sexual identity and behavior.