Economic Consequences of Kinship: Evidence From U.S. Bans on Cousin Marriage.

The article investigates the causal effects of weakening kinship ties through bans on first-cousin marriage in nineteenth- and early twentieth-century U.S. states, using excess same-surname marriages (marital isonymy) as a proxy for cousin marriage rates. Analyzing millions of marriage records and census data from 1850 to 1940, the study finds that cousin marriage bans led to increased geographic dispersion, rural-to-urban migration, higher occupational mobility, and improved incomes among men from families with historically high cousin marriage rates. These changes appear driven by social and cultural shifts weakening kinship bonds rather than genetic health improvements or changes in inheritance patterns. The findings align with anthropological theories that intensive kinship structures, reinforced by cousin marriage, promote cooperation but limit mobility and economic modernization, suggesting that loosening such ties facilitated structural economic transformation in the United States.