Study finds that marriage age gaps rose between 1850 and 1880; gaps ranged from 4 to 7 years on average.
Karen Rolf, Joseph P. Ferrie, "The May-December Relationship since 1850: Age Homogamy in the U.S.," Working paper, March 7, 2008, 2-4, 12
We find that the gap between husbands’ and wives’ ages actually rose from 1850 until 1880 (Figures 1 and 2), before it began its twentieth century decline. This is true for both the entire population 3 (Figure 1) and for the native-born white population (Figure 2). The pattern for the second half of the nineteenth century also persists is we look at birth cohorts rather than census years, and if we consider new marriages in the year preceding the census rather than the entire stock of marriages in existence at the time of the census.
[Figures 1 & 2]
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[Table 3]