Immigration has become a salient political issue not only in the United States but also in Australia, Canada, and many European countries, all of which are struggling with the issues of selective admission and mass exclusion. Here an American economist and an Australian economist collaborate to provide a breathtaking survey of world migration, and the policies pertaining thereto, over two centuries. They focus especially on the mass migrations of the late nineteenth and late twentieth centuries (and on the sharp decrease in the mid-twentieth century). They insist on the importance of economic factors both in motivating the migrants and in assessing the impact on receiving countries. In particular, a sharp decline in transport costs with the arrival of the oceangoing steamship and the railroad, combined with enough increased income in the sending countries to enable people to emigrate, stimulated the flood of long-distance migration in the late nineteenth century. They also analyze the factors, especially perceived declines in the skill levels of immigrants and immigrants' depressing effect on low-skill wages, that led gradually to a tightening of immigration policy in receiving countries from the extreme openness that prevailed in midcentury. Much historical work on migration focuses on the great transatlantic European migrations; this book takes a broader view, reporting also on the emigration of millions of Indians and Chinese in the nineteenth century and of Africans in the twentieth. And it also provides an extensive bibliography for those who want to pursue in greater detail particular episodes or theories of migration and its effects.