Trends in assortative mating in the United States, 1700-1910. Evidence from FamiLinx data.

Couple formation and assortative mating significantly influence societal structures, as marriages between individuals from diverse geographical or social backgrounds promote intra-family diversity. Understanding these patterns is crucial for grasping the demographic processes that shape contemporary societies. However, the scarcity of comprehensive data has impeded progress in this area. This paper aims to fill this gap by investigating assortative mating trends in the United States among birth cohorts from 1700 to 1910, utilizing data from FamiLinx, an online crowdsourced genealogical database. We focus on two primary dimensions: migration background (including natives, first and second-generation migrants) and age at marriage. Our analysis yields three major findings. First, we document significant changes in assortative mating trends over time, reflecting the dynamic nature of mate selection and its responsiveness to societal shifts. Second, we uncover substantial heterogeneity in assortative mating patterns across different social groups, indicating varying social dynamics and preferences. Third, we illustrate how these trends can be differently interpreted depending on whether the perspective is individual or familial. Additionally, we explore the advantages and limitations of using online genealogical data for historical studies of assortative mating, highlighting its potential for offering new insights while acknowledging the challenges posed by data quality and representativeness.