“…An additional 4.5 million moved during the second wave, from 1940 to 1970 (Census, 1979, Table 8). A key motivation for these migrants was better labor market opportunities (Scott, 1920;Henri, 1975;Gottlieb, 1987;Grossman, 1989;Marks, 1989;Gregory, 2005;Wilkerson, 2010). Manufacturing employment, which opened to Black workers with the onset of World War I, was an especially attractive pull factor, while declining opportunities in agriculture pushed migrants out of the South (Boustan, 2010).…”