Exodus: How Migration is Changing Our World (titled Exodus: Immigration and Multiculturalism in the 21st Century for its UK release) is a 2013 book by the development economist Paul Collier about the way migration affects migrants as well as the countries that send and receive the migrants, and the implications this has for development economics and the quest to end poverty. It was published by Oxford University Press. Collier's book focuses on the challenges posed by the nexus of immigration and multiculturalism, and also claims that brain drain is one of the main, often overlooked, drawbacks of migration. According to Colin Kidd, Collier argues that Western immigration policy has been driven not by reason, but by emotional responses to postcolonial Western guilt "while stifling considera