The findings, released Thursday, were based on interviews with more than 121,000 people. Gallup said it is the largest study ever aimed at calculating the nation's LGBT population.
The report's lead author, demographer Gary Gates of the UCLA School of Law's Williams Institute, said he hoped the findings would help puncture some stereotypes about gays and lesbians while illustrating the diversity of their community.
"Contemporary media often think of LGBT people as disproportionately white, male, urban and pretty wealthy," he said. "But this data reveal that relative to the general population, the LGBT population has a larger proportion of nonwhite people and clearly is not overly wealthy."
According to the survey, which was conducted between June and September, 4.6 per cent of African-Americans identify as LGBT, 4 per cent of Hispanics, 4.3 per cent of Asians and 3.2 per cent of whites. Overall, a third of those identifying as LGBT are nonwhite, the report said.
There was a slight gender difference — 3.6 per cent of women identified as LGBT, compared to 3.3 per cent of men. And younger adults, aged 18 to 29, were more likely than their elders to identify as LGBT.
One striking difference: among 18-to-29-year-olds, 8.3 per cent of women identify as LGBT, compared with 4.6 per cent of men the same age.
The survey also asked about political leanings: it found that 44 per cent of the LGBT adults identified as Democratic, 43 per cent as independent, and 13 per cent as Republican. In contrast to Gallup polling showing an overall even split between President Barack Obama and his Republican challenger, Mitt Romney, the survey found 71 per cent of LGBT registered voters supporting Obama, and 22 per cent supporting Romney.
In contrast to some previous, smaller studies, the Gallup survey found that identification as LGBT is highest among Americans with the lowest levels of education. Among those with a high school education or less, 3.5 per cent identify as LGBT, compared with 2.8 per cent of those with a college degree and 3.2 per cent of those with postgraduate education.
A similar pattern was found regarding income groups. More than 5 per cent of those with annual incomes of less than $24,000 identify as LGBT, compared to 2.8 per cent of those making more than $60,000 a year.
Among those who report income, about 16 per cent of LGBT individuals have incomes above $90,000 per year, compared with 21 per cent of the overall adult population, the Gallup survey found. It said 35 per cent of those who identify as LGBT report incomes of less than $24,000 a year, compared to 24 per cent for the population in general.
Regarding family status, 20 per cent of LGBT individuals said they are married and an additional 18 per cent are living with a partner; they weren't asked about the gender of those spouses and partners. Among non-LGBT Americans, 54 per cent are married and 4 per cent are living with a partner, the report said.
The survey found that 32 per cent of both LGBT and non-LGBT women have children under 18 in their home. By contrast, 16 per cent of LGBT men had children in their home, compared to 31 per cent of non-LGBT men.
Gates said he was struck by the geographical spread of the LGBT population — pegged at 3.7 per cent in the East, 3.6 per cent in the West, 3.4 per cent in the Midwest and 3.2 per cent in the South.
The results were based on responses to the question, "Do you, personally, identify as lesbian, gay, bisexual, or transgender?" included in 121,290 Gallup interviews conducted between June 1 and Sept. 30.
The overall 3.4 per cent figure is similar to a 3.8 per cent estimate made previously by Gates after averaging a group of smaller U.S. surveys conducted from 2004 to 2008.
The survey noted that its findings did not account for LGBT people who, for whatever reason, did not want to acknowledge their sexual orientation in the interviews.
The Gallup report: http://bit.ly/Rb0PAX
David Crary can be followed on Twitter at http://twitter.com/CraryAP