Assortative matching among same-sex and different-sex couples in the United States, 1990-2000.

Same-sex couples are less likely to be homogamous than different-sex couples on a variety of characteristics including race/ethnicity, age, and education. This study confirms results from previous studies which used 1990 U.S. census data and extends previous analyses to examine changes from 1990 to 2000. We find that same-sex male cohabitors are generally the least likely to resemble one another, followed by same-sex female cohabitors, different-sex cohabitors, and different-sex married couples. Despite estimated growth in the numbers of same-sex couples in the population and the increasing acceptance of same-sex unions, we find little evidence of diminishing differences in the resemblance of same- and different-sex couples between 1990 and 2000, with the possible exception of educational homogamy.