The world currently has around 260 million international migrants, that is, people who live in a country different from the one in which they were born. Out of these, around 90 million have moved to the richer Western world (Europe, North America, Australia, New Zealand) from the mostly poorer rest of the world. This corresponds to approximately 1.5 percent of the population in the part of the world they have left, and about 10 percent in the part to which they have moved. Each year over the last few decades, their number has increased on average by around two million.

This book is about this migration. Some of it happens because people are forced to flee from war or persecution in their home country, or for family reasons. Yet most migrants move for predominantly economic reasons. They move to enhance their living standards, or at least for an opportunity to do so. Roughly estimated, an average migrant from the rest of the world has increased their annual income by more than US$10,000 by migrating to the West (see Chapter 7). Multiplied by 90 million migrants, this implies a considerable increase in global living standards. A part of this income is also sent to relatives in the migrants’ home countries, contributing to improved living standards there as well.

The vast economic consequences of migration for people who were born in low-and middle-income countries are thus evident. They are commonly seen as mostly positive, although there are also fears that some of these countries may have lost too many of their most talented and educated people, whom they would have needed for creating better economic development at home.

Yet in the receiving countries, migration leads to more far-reaching and polarizing conflicts than perhaps any other political issue of today. Many feel warmly about migration, because it gives others possibilities to improve their lot through their own sacrifices and hard work, or allows them to escape war and persecution. Many others worry about how migration impacts labor market opportunities for those who have already been hit by decades ofdeindustrialization, automation and increasing demands on workforce skills; about migration draining public finances; harming national identity, cohesion, community, trust or communication and understanding between people— ultimately about the risk of migration harming the very foundation of society, which is people's shared willingness to constitute one.