The national attention received by Dyer's anti-lynching bill and speaking campaign may have helped reduce lynchings in the South. More significantly, the Great Migration was underway, and black workers by the tens of thousands were leaving the South for Northern and Midwestern industrial cities, for jobs, education, and a chance to escape Jim Crow laws and violence. By 1934, when the Costigan-Wagner anti-lynching bill was introduced, lynchings had dropped to 15 per year. In 1935 and 1938, Senator Borah repeated his constitutional arguments against the bill; he added that he believed such legislation was no longer needed, because the rate of lynchings had fallen so dramatically. By 1940, 1.5 million blacks had left the South in the Great Migration. Another five million left from 1940 to 1970.