Close-kin marriage, by sustaining tightly knit family structures, may impede development. We find support for this hypothesis using U.S. state bans on cousin marriage. Our measure of cousin marriage comes from the excess frequency of same-surname marriages, a method borrowed from population genetics that we apply to millions of marriage records from the eighteenth to the twentieth century. Using census data, we first show that married cousins are more rural and have lower-paying occupations. We then turn to an event study analysis to understand how cousin marriage bans affected outcomes for treated birth cohorts. We find that these bans led individuals from families with high rates of cousin marriage to migrate off farms and into urban areas. They also gradually shift to higher-paying occupations. We also observe increased dispersion, with individuals from these families living in a wider range of locations and adopting more diverse occupations. Our findings suggest that these changes were driven by the social and cultural effects of dispersed family ties rather than genetics. Notably, the bans also caused more people to live in institutional settings for the elderly, infirm, or destitute, suggesting weaker support from kin.

中文翻译：

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亲属关系的经济后果：美国禁止表亲结婚的证据

通过维持紧密结合的家庭结构，近亲婚姻可能会阻碍发展。我们通过美国各州禁止表亲结婚找到了对这一假设的支持。我们衡量表亲婚姻的依据是同姓婚姻的频率过高，这是一种从人口遗传学中借用的方法，我们将其应用于从 18 世纪到 20 世纪的数百万婚姻记录。使用人口普查数据，我们首先表明已婚堂兄弟姐妹更多地居住在农村并且从事低薪职业。然后，我们转向一项事件研究分析，以了解近亲婚姻禁令如何影响接受治疗的出生队列的结果。我们发现，这些禁令导致表亲结婚率高的家庭中的个人从农场迁移到城市地区。他们也逐渐转向高薪职业。我们还观察到色散增加，这些家庭中的个人居住在更广泛的地点并从事更多样化的职业。我们的研究结果表明，这些变化是由分散的家庭关系的社会和文化影响而非遗传驱动的。值得注意的是，这些禁令还导致更多人住在养老院、体弱者或赤贫者的机构中，这表明来自亲属的支持较弱。