A: None, according to the U.S. Census
Why? A New York Times article on July 18 quotes Steven H. Murdock, director of the U. S. Census Bureau, who explains that because of the 1996 Defense of Marriage Act marriages between people of the same sex cannot be recognized or counted even in the states where they are legal. Even by the Census.
Why does it matter? Gay rights activists argue that it matters because it renders married same-sex couples invisible. I agree. That absolutely matters. But it also matters because it is evidence of our government's blinding itself to reality. It is further evidence, as with interference in climate research and health research, that the government cannot be trusted to put science and reason ahead of ideology, religion and faith.