Increases in sex with same-sex partners and bisexual identity across cohorts of women (but not men)

We use data from the 2002-2013 National Surveys of Family Growth to examine change across U.S. cohorts born between 1966 and 1995 in whether individuals have had sex with same-sex partners only, or with both men and women, and in whether they have a bisexual or gay identity. Adjusted for age, race/ethnicity, immigrant status, and mother's education, we find increases across cohorts in the proportion of women who report a bisexual identity, who report ever having had sex with both sexes, or who report having had sex with women only. By contrast, we find no cohort trend for men; roughly 5 percent of men in every cohort have ever had sex with a man, and the proportion claiming a gay or bisexual attraction changed little. We speculate that this gender difference is rooted in a broader pattern of asymmetry in gender change in which departures from traditional gender norms are more acceptable for women than men.