The Geography of Same-Sex Marriage in the U.S.

The decision by the U.S. Supreme Court that same-sex marriages are legal has, of course, raised the profile of this type of family and household arrangement. However, there aren't a lot of data on the number and characteristics of such households, so the story by Quoctrung Bui in today's NYTimes Upshot was very revealing. He summarizes an analysis done by three researchers at the U.S. Treasury Department--Robin Fisher, Geof Gee, and Adam Looney.

By linking the tax returns of same-sex couples who filed jointly in 2014 with their Social Security records, researchers are able to give us the most accurate picture of same-sex marriages to date. And their estimate is this: In 2014 there were 183,355 same-sex marriages in America, roughly a third of 1 percent of all marriages.

Of course, implicit in this estimate is the assumption that all married couples file their returns jointly. But as a proxy for that, it’s pretty good. The Treasury Department estimates that 97.5 percent of married couples file joint returns.

The results offer the interesting, but not unexpected finding that male same-sex married partners have higher incomes than female same-sex married partners. The usual explanations apply--women earn less than men, and female marriages are much more likely than male marriages to involve children, and the competition between children and a career means that one parent may work less and thus earn less.

The geography of same-sex marriages shows a pattern in which the percentage of married couples filing joint tax returns who are same-sex couples is highest along the two coasts and lower in the middle of the country. Not surprisingly, the San Francisco Bay Area has the highest percentage of same-sex couples, although males are highest in San Francisco, while females are highest across the bay in Oakland. The map below is static, by the way, whereas the published map is interactive and gives you details for grouped zip codes.