Shankar Vedantam writes for The Washington Post: “About 24,000 gay and lesbian couples in the United States include at least one foreign partner, according to an analysis of census data by researcher Gary Gates at UCLA’s Williams Institute. Though five states and D.C. issue marriage licenses to gay couples, a large number of the 24,000 so-called binational couples in long-term relationships live in states that do not allow or recognize gay marriage.”