As this map on The Economist website shows, the highest concentration of households headed by gay couples, according to U.S. Census data, are in states that recognize same-sex partnerships or marriage. According to the Williams Institute, a gay rights think-tank at UCLA, D.C. has the highest proportion of gay households in the country, with 14 for every 1,000 headed by same-sex couples. (The national average is 4.7.) Though Maine has the second highest concentration, with more than eight same-sex households for every 1,000, that could soon change: voters recently decided to repeal legislation recognizing gay marriage. And as the map indicates, gay couples are least likely to live in the heartland, which is also a Republican stronghold.