“…In advancing our understanding of assimilation in the Age of Mass Migration, this paper complements research byHatton and Williamson (1998),Ferrie (1999),Abramitzky, Boustan, and Eriksson (2014),Abramitzky et al (2019b),Zimran (2019), andPérez (2019), among others Abramitzky and Boustan (2017). andHatton and Ward (2019) survey this literature.9 We focus on European migration because it accounts for nearly 90 percent of the total inflows to the US prior to 1914 (Abramitzky and Boustan 2017, Figure2, p. 1316), because it was the subject of the main policy debates in the nineteenth and twentieth centuries, and because it was effectively unconstrained prior to World War I (as opposed to Asian immigration, which was effectively banned by the Chinese Exclusion Act of 1882 and the "Gentlemen's Agreement" of 1907).…”