If you look at the graph above, you notice two things. First, that for several years the percent of states that allowed gay marriage (out of 51, once we included DC) tracked higher than the percent of the population that lived in same-sex marriage states. That's because it was small states that moved on it first: Connecticut, Iowa, Vermont, New Hampshire. (And, yes, Massachusetts.) Now, the percent of the population that lives in gay marriage states tracks more closely with the percent of the population overall.