Increased Support for Same-sex Marriage in the US: Disentangling Age, Period, and Cohort Effects

Previous research established a substantial increase in support for same-sex marriage in the US, but it is unclear if this increase is due to cohort (a change that affects only the younger generation) or time period (a change that affects those of all ages). In a nationally representative sample of American adults (n = 13,483) in 1988 and 2004–2018, increased support for same-sex marriage was primarily due to time period (from 11.1% in 1988 to 66.7% in 2018). There was a smaller cohort effect, with a fairly linear increase between cohorts born in the 1960s and those born in the 1990s. Time period increases in support for same-sex marriage appeared among across gender, race, education levels, regions, and levels of religious service attendance, though differences in support still remain. The results suggest Americans of all ages modified their beliefs about same-sex marriage over time.