"Most labor scarce overseas countries moved decisively to restrict their immigration during the first third of the 20th century. This autarchic retreat from unrestricted and even publicly-subsidized immigration in the first global century before World War I to the quotas and bans introduced afterwards was the result of a combination of factors: public hostility towards new immigrants of lower quality public assessment of the impact of those immigrants on a deteriorating labor market, political participation of those impacted, and, as a triggering mechanism, the sudden shocks to the labor market delivered by the 1890s depression, the Great War, postwar adjustment and the great depression. The paper documents the secular drift from very positive to much more negative immigrant selection which took place in the first global century after 1820 and in the second global century after 1950, and seeks explanations for it. It then explores the political economy of immigrant restriction in the past and seeks historical lessons for the present"--National Bureau of Economic Research web site.