The purpose of this book

The growing importance of international migration

Migration flows around the world have increased rapidly in recent decades. The immigrant population in OECD countries has more than tripled since the 1960s. According to the United Nations (2009), some 3 per cent of the world's people lived in a country other than the one they were born in in 2010.

Geographical mobility is an old phenomenon, but international migration has grown in volume and significance since 1945, particularly since the mid-1980s. As Castles and Miller (2009: 10-12) claim, one of the most distinctive traits of the migration movements in recent decades has been their global scope. An increasing number of countries has been involved in migratory movements, and at the same time the division between migrantsending and migrant-receiving states is blurring. Compared to previous waves of migration, the current movements of populations across countries are more diverse in terms of migrants’ economic, social, cultural and political backgrounds, producing more differentiation of migration, and amplifying its potential social, cultural and political impact in receiving countries.

Immigration has become a salient issue on the political agenda in many countries. This has led to an increasing demand for data, not only regarding flows of populations between countries, but also related to the characteristics and living conditions of migrants within countries (as well as their integration). This need to monitor population settlements is not new. As Reeger and Sievers (2009: 297) point out, the desire to have control over the population residing in a given territory and even the word ‘statistics’ are very much linked to the development of the nation-state in the nineteenth century, though some of the tools used by statisticians, such as censuses, were already in use in ancient civilisations. However, censuses cannot satisfy the current demand for information, and surveys have become the most widely used data-collection tool. This book deals with the technical and methodological challenges that surveying immigrant populations entails and how to confront them. Before addressing these challenges, thenext section looks in more detail at the demand for data with which these surveys are trying to comply.