Immigration is a hotly discussed topic, with emotions and ideology usually trumping a careful reading of data on the actual numbers of those moving across borders. Paul Collier‘s Exodus focuses on the factors that affect people’s decisions to migrate, how immigration affects those left behind, and how it shapes societies in host countries. Collier, a respected development economist at Oxford and former director of research at the World Bank, is not a migration expert per se, and the book does not offer much in terms of new empirical results. Instead, it provides the reader with a simple theoretical model of migration, informed by microeconomic theory, and a review of existing applied research in the area, alongside some rather strong policy claims.
The book is targeted at a general audience but also at those in the policy community who wish to acquire a more systematic understanding of the mechanics of migratory flows and its social and economic effects. Across twelve chapters the book focuses on the effects of immigration on host societies (part two), its implications for migrants themselves (part three) and for their home countries (part four). Finally, the book draws conclusions regarding desirable migration policies in the West (part five).
At the heart of the book lies a simplified model of migration, linking migration to the size of the diaspora: the larger the diaspora, the easier is immigration. Simultaneously, a sizeable diaspora slows down the absorption of immigrants into mainstream society. Consequently, under certain conditions, unrestricted immigration can lead to an explosive growth in immigrants, increasing the diaspora and stalling integration. The effect of an explosive growth in the number of immigrants, discussed in chapter 3, is probably the most important — and most controversial — contribution of the book.
Collier argues that large and culturally distinct diasporas reduce the levels of trust and cooperation in the host societies, citing research by Robert Putnam, a Harvard scholar specialising in the study of social capital. Lower trust levels erode the ability of governments to redistribute income: “despite a growing need for redistributive policies, actual policies have shifted in the opposite direction,” Collier states. But the claim that government redistribution is on the retreat is difficult to reconcile with that fact that, as a fraction of GDP, government spending in the United States is higher than it was in the 1970s. In the United Kingdom, it is roughly at the same level as in 1979.