[Cross-posted at the Gay Couples Law Blog, which discusses same sex family law and estate planning.] 

In 2010, for the first time, the U.S. Census will count same sex marriages, publishing the number the following year.

The Washington Post discussed on Sunday why the published numbers will be important for gay rights advocates:

Particularly at the state and local levels, gay advocacy groups say census data on income for same-sex couples will show the need for more protections against job discrimination. Statistics on households with children will help them challenge laws limiting gay adoptions and legal guardianship. With raw numbers to illustrate the need, it will be easier to demand services, they say.

Yet the number of married gay couples will probably include many couples that aren't actually married. That's because same sex couples in states where marriage is unavailable will likely call themselves married anyway.

No states allowed gay marriage back in 2000. Yet almost half of all same sex couples identified in the 2000 census as married. The 2000 census even offered an “unmarried partner” option,” but so many couples checked the spouses box regardless.

Similarly, the 2007 American Community Survey, a smaller operation of the U.S. census, reported over 300,000 same sex marriages, although only around 10,000 gay couples had actually been legally married, all in Massachusetts.

Therefore, as the Post article notes, in the 2010 census, “demographers expect hundreds of thousands to report they are spouses — even though legal same-sex weddings in the United States number in the tens of thousands.”

This may just be an unexpected result the general unavailability of same sex marriage. Perhaps gay couples that want to, but cannot, get married nevertheless self identify as spouses to say, “We're not married, but we would be if we could.”