More than 1,300 same-sex couples in Minnesota described themselves as married in 2010, even though the state does not recognize such marriages, the U.S. Census Bureau said Tuesday in its first attempt to measure the phenomenon.

At the same time, federal officials admitted that the 2010 census badly overestimated the number of same-sex couples in Minnesota and nationally.

The original census data counted 4,325 same-sex couples who identified themselves as married and living together in Minnesota -- three times higher than the revised figure. The original census data also counted 13,718 same-sex couples living together in Minnesota, regardless of marital status, while the revised estimate is now only 10,207.

The revisions probably do little to change Minneapolis' status as one of the more attractive destinations for same-sex couples between the coasts. The city ranks seventh among the nation's 50 largest cities for the number of same-sex couples relative to its overall population.

Even the revised numbers remain subject to scrutiny, given the ambiguity of the issue and shifting social attitudes, said Monica Meyer, executive director of OutFront Minnesota, a GLBT advocacy group.

Despite a more accepting climate for gay couples, there still may be those who didn't acknowledge their marital status on the census form, especially if they were providing the information to a door-to-door census taker, she said.

"I bet people went two different ways on that," she said. "For some couples, it was like 'Definitely, we're checking married because we are married.'"

It's unclear from the data how many of the Minnesota couples were married in states that recognize the unions but didn't identify themselves as married because Minnesota does not have legal recognition -- and how many are not legally married but chose to identify themselves as married for symbolic reasons.

Not counted in the marriage column were Leslie Sandberg of Minneapolis and her spouse, Kass Goodwin, who were married at a September 2010 ceremony in Massachusetts. Sandberg completed the census form a few weeks before the ceremony. A former spokeswoman for the Minnesota attorney general's office, Sandberg said she chose strict accuracy in filling out the form.

"I've always opted to be someone who played by the rules," she said. "We did discuss [putting down that we were married] and we thought, 'No. If we're going to do it, we're going to do it the right way."

Overcount

The original 2010 census overestimated the number of same-sex-couple households in Minnesota by 25 percent, but the national error rate was worse -- 28 percent. Errors crept into the census data primarily when people failed to mail in their census forms and federal workers instead interviewed them door to door, explained Martin O'Connell of the Census Bureau.

Minnesota had the nation's second-highest census participation rate last year, so the state had more forms completed by mail and fewer completed by door-to-door census workers.

Problems with census forms completed door to door ranged from inconsistent judgments by census takers pertaining to the genders of people with unusual names, and the confusing, multiple-page layout of the forms that they used to collect information.

Despite the overcount in the original 2010 census, the figures released Tuesday reveal illuminating patterns among same-sex-couple households. Members of one in five same-sex couples nationwide identified themselves as spouses, according to the revised 2010 figures. That rate rose to 33 percent in Iowa, where same-sex marriages are recognized. The rate in Minnesota was 13 percent -- fourth-lowest in the nation.

Census officials suspected a problem in the 2010 figures early on, because the numbers differed substantially from the American Community Survey that was also collected that year.

To confirm the inaccuracies, census researchers compared the genders of census respondents from supposedly same-sex households to an index of names. They found many instances of people with names that are almost always male or female that had been classified with the wrong gender, creating the impression of same-sex households that in fact were opposite-sex households.

The revised data suggest there are thousands fewer same-sex-couple households that can provide political clout to organizations such as OutFront Minnesota, which is fighting a proposed constitutional amendment to outlaw gay marriage and fighting for explicit laws to prohibit bullying due to sexual orientation.

Meyer said the census doesn't offer a full picture of the gay population in Minnesota because it doesn't identify single people by their sexual orientation -- only couples living together.

Sandberg said a drop in the relatively small number of gay couples in Minnesota won't make a significant difference in the upcoming vote on the constitutional amendment, because the outcome will depend on the majority viewpoint.

"Like a lot of civil rights battles," she said, "any minority group can't do it on its own."