Breakthroughs in Historical Record Linking Using Genealogy Data: The Census Tree Project

The Census Tree is the largest-ever database of record links among the historical U.S. censuses, with over 700 million links for people living in the United States between 1850 and 1940. These high-quality links allow researchers in the social sciences and other disciplines to construct a longitudinal dataset that is highly representative of the population. In this paper, we describe our process for creating the Census Tree, beginning with a collection of links contributed by the users of a free online genealogy platform. We then use these links as training data for a machine learning algorithm to make new matches and incorporate other recent efforts to link the historical U.S. censuses. Finally, we introduce a procedure for filtering the links and adjudicating disagreements. Our complete Census Tree achieves match rates between adjacent censuses that are between 69 and 86% for men, and between 58 and 79% for women. To demonstrate the advantages of the Census Tree, we extend the work of Abramitzky, Boustan, Jácome, and Pérez (2021) to include intergenerational mobility estimates for additional immigrant nationalities and for women.