Background: Research into the causes of the mid-20th-century baby boom has concluded that the main proximate cause of the fertility increase during the 1940s was earlier and more universal marriage in the cohorts born after 1910, and that this association between nuptiality trends and fertility was particularly strong in Sweden.

Objective: However, we do not know whether this was a general trend or if certain socioeconomic groups spearheaded the change toward earlier marriage.

Methods: The present study uses event history analysis to investigate the marital histories of approximately 100,000 men and women in Sweden, born 1880–1934, to determine how socioeconomic differentials in nuptiality developed during the period 1900–1960.

Conclusions: The analysis shows that the sharp increase in nuptiality was not driven uniformly across different social strata, but rather took the form of earlier and more universal marriage among men in the mid and upper social strata and among economically active women, while male unskilled workers and women outside the labor market did not participate in the nuptiality boom during the peak baby boom years and even showed some signs of decreased marriage probabilities compared to earlier cohorts.

Contribution: The results indicate that sector-specific economic growth after the depression and the breakthrough of the Swedish welfare state benefitted couples who could aspire to a middle-class identity, and that pronatalist policies made female economic activity more compatible with marriage. The results show that the shift toward a positive female socioeconomic gradient of marriage and family formation that can be observed in contemporary Sweden had its beginnings already with the cohorts that participated in the mid-20th-century baby boom.