Unmarried Partners Make Up 6% of U.S. Households 

According to data collected from the 2010 census, nearly 6.5 million unmarried partners live together in the United States -- roughly 6% of the population.

That number isn't specific to gay couples -- more information on unmarried partners will be released in June, followed by statistics specifically on same-sex couples in November.

The latest round of findings from the census also shows that Washington, D.C., has the greatest number of same-sex, unmarried partner households per capita at 2%.