Despite the end of the Cold War, the world does not lack sources of insecurity. Mass migration -- often a product as well as a cause of unrest -- is one example, as recent events in Africa show. And instability lies not just with the movement of immigrants but with the politics of exile communities as well. To his credit, Van Hear defines diasporas with fair precision: the dispersion of a people from a homeland to two or more territories, with an enduring presence abroad and exchanges among the scattered communities. However, the writing is stilted and the subject does not always lend itself to easy comparisons. Still, the analysis remains useful by including some basic statistics in its systematic presentation of modern mass migration.