SAN FRANCISCO -- Same-sex couples who identify as married are similar to straight spouses in terms of age and income, and nearly one-third of them are raising children, according to Census data released Monday that provides a demographic snapshot of gay families in America.

The study released by a think tank based at UCLA also found that Utah and Wyoming were among the states with the highest percentages of gay spouses in 2008, despite being heavily conservative states with no laws providing legal recognition of gay relationships.

The data from the annual American Community Survey showed that nearly 150,000 same-sex couples in the U.S., or more than one in four, referred to one another as "husband" or "wife," although UCLA researchers estimate that no more than 32,000 of the couples were legally married.

The couples had an average age of 52 and household incomes of $91,558, while 31 percent were raising children. That compares with an average age of 50, household income of $95,075 and 43 percent raising children for married heterosexual couples.

"It's intrinsically interesting that same-sex couples who use the term spouses look like opposite-sex married couples even with a characteristic like children," said Gary Gates, the UCLA demographer who conducted the analysis. "Most proponents of traditional marriage will say that when you allow these couples to marry, you are going to change the fundamental nature of marriage by decoupling it from procreation. Clearly, in the minds of same-sex couples who are marrying or think of themselves as married, you are not decoupling child-rearing from marriage."

Gates said the report is the first to reliably compare same-sex couples who identify as married with gays who say they're in unmarried partnerships and with married opposite-sex couples.

In the past, same-sex couples who referred to one another as "husband" or "wife" automatically were recorded as unmarried partners, a step gay rights activists lobbied the Census Bureau to eliminate as more states have legalized same-sex unions.

Unsurprisingly, Massachusetts, where gay couples have been able to get married since 2004, had the highest proportion of same-sex couples who were either legally married or considered themselves married, 3.63 for every 1,000 households. Vermont, which allowed same-sex couples to enter in civil unions with all the rights and obligations of marriage in 1999 and made same-sex marriages legal this year, came in second, with a rate of 2.71 per 1,000.

But Hawaii, Utah and Wyoming -- states with neither civil unions nor same-sex marriage -- came in next, ahead of California, Nevada, Connecticut, New Jersey and Rhode Island. What accounts for the phenomenon is unclear, but "it does provide this evidence that there are clearly couples in conservative parts of the country who do use these terms and do see their relationships in that framework."

Melissa Bird, a 35-year-old Utah lobbyist, said she understood why her home state has so many same-sex couples who see themselves as married, even though the state government does not recognize them that way. Bird and her 26-year-old partner had a commitment ceremony two years ago in Utah that wasn't legally binding. They tied the knot legally in California last year before voters approved a gay marriage ban.

"There is very much a marriage mentality here in Utah," said Bird, whom considers her partner her wife. "We know a lot of people who get 'married' in quotes. It never crossed our minds not to do it."

Once same-sex couples who labeled themselves as unmarried partners were factored in, however, the geographic distribution changed significantly. The District of Columbia came in first, with same-sex couples -- both unmarried partners and those who called themselves married -- representing 14.12 of every 1,000 households. Maine, where voters on Tuesday will decide whether to repeal a law that legalized same-sex marriage, was next, with gay couples heading up a little more than eight of every 1,000 households.

Although the report includes the first official estimates for the number of same-sex couples who call themselves wives or husbands, Gates said collecting accurate data on the marital status of gay couples remains difficult because of the hodgepodge of laws affecting their relationships. In addition, many couples may be reluctant to identify themselves as such if their neighbors, families and employers do not know they are gay, he said.

The Census Bureau has promised to produce a report on the marital status of gay couples after the once-a-decade national census is completed next year. However, the bureau said there was too little time to change the questionnaire to separate out legally married gay couples in the nationwide tally.