The end of endogamy?:Two centuries of kin marriage in The Netherlands (1812-2021)

Prior research on consanguinity and kin marriage in Western societies has remained surprisingly silent on the postwar period, when kin endogamy is often believed to have become completely obsolete. In this study, we combine historical and contemporary data to chart and understand long durée changes in the incidence of different types of kin marriage in the Netherlands from the 1840s until today. Our study shows that cousin marriages comprised 2.7% of all unions during the 1871-1880 period and decreased to approximately 1.5% during the 1911-1922 period. Sibling set exchange marriages peaked at 4.7% in the last decade of the nineteenth century, after which they declined to 2.8% between 1911-1922. Surprisingly, despite this overall decline, a slight resurgence in sibling set exchange partnerships occurred in the 1970s and 1980s among the members of the baby boom generation. Moreover, cousin marriages saw a slight rise among those born in the 1970s, possibly partly as a result of import marriages among migrant groups. Kinship availability, religious-ideological group formation, and class- and education-based assortative mating explain these different trends, often reinforcing each other, and thereby producing specific spatial patterns of kin marriage. Our findings show that trends and patterns of kin endogamy were highly path-dependent and may wax and wane conditional on historical circumstances.