Such a misunderstanding of the basic demographics of sexual behavior and identity in America has potentially profound implications for the acceptance of the gay-rights agenda. On the one hand, people who overestimate the percent of gay Americans by a factor of 12 seem likely to also wildly overestimate the cultural impact of same-sex marriage. On the other hand, the extraordinary confusion over the percentage of gay people may reflect a triumph of the gay and lesbian movement's decades-long fight against invisibility and the closet.

"My first reaction to that, aside from a little chuckle, is that it's actually a sign of the success of the movement for LGBT rights," said Stuart Gaffney, a spokesman for the group Marriage Equality USA. "We are a small minority, and we will never have full equality without the support of the majority, and a poll like that suggests the majority is extremely aware of their gay neighbors, coworkers, and friends."

In recent years, as homosexuality has become less stigmatized, pro-gay rights groups have come around to acknowledging that a smaller percent of people identify themselves as gay than some of the early gay rights rhetoric claimed, based on Alfred Kinsey's 1948 report, "Sexuality in the Human Male." His survey research on non-random populations in the immediate post-World War II period concluded that 10 percent of men "were predominantly homosexual between the ages of 16 and 55" and that 37 percent had had at least one homosexual experience in their lives, but did not get into questions of identity per se.

Contemporary research in a less homophobic environment has counterintuitively resulted in lower estimates rather than higher ones. The Williams Institute at UCLA School of Law, a gay and lesbian think tank, released a study in April 2011 estimating based on its research that just 1.7 percent of Americans between 18 and 44 identify as gay or lesbian, while another 1.8 percent -- predominantly women -- identify as bisexual. Far from underestimating the ranks of gay people because of homophobia, these figures included a substantial number of people who remained deeply closeted, such as a quarter of the bisexuals. A Centers for Disease Control and Prevention survey of women between 22 and 44 that questioned more than 13,500 respondents between 2006 and 2008 found very similar numbers: Only 1 percent of the women identified themselves as gay, while 4 percent identified as bisexual.

Higher numbers can be obtained when asking about lifetime sexual experiences, rather than identity. The Williams Institute found that, overall, an estimated 8.2 percent of the population had engaged in some form same-sex sexual activity. Put another way, 4.7 percent of the population had wandered across the line without coming to think of themselves as either gay or bisexual. Other studies suggest those individuals are, like the bisexuals, mainly women: The same CDC study that found only 1 percent of women identify as lesbian, for example, found that 13 percent of women reported a history of some form of sexual contact with other women.