ABSTRACT
In many European countries international migration is now the most important component of population change; in a large number of countries within the European Economic Area1 net migration accounts for more than 50 percent of total population increase in recent years (Salt and Singleton, 1995). In the period from 1985 to 1993 the total number of immigrants into the EEA countries increased from 0.9 million to 2.6 million persons (ICMPD, 1994). These people are not only registered immigrants; the number of asylum seekers, displaced persons from former Yugoslavia and illegal immigrants constituted in 1993 almost 50 percent of the total inflow into the EEA. Although the causes of international migration in general are well
studied and there is agreement with regard to the most important factors determining the migration flows between countries, until now there has been hardly any attempt to link these theoretical considerations with empirical data on international migration flows. The limited use of migration flow data is partly due to the problem of measuring international migration. The measurement of international migration is problematic for various reasons. First, data are not consistent between countries. Flows between countries are usually recorded both by the sending and the receiving country, but these figures are often inconsistent. Second, there is no agreement among countries over the proper definition of a migrant. Third, not all immigration is registered. Especially illegal immigration is hard to measure. Consequently, a consistent system of international migration statistics has been lacking until now. Only recently, attempts are being made in this direction; a process that involves both methodological (Poulain 1991; Willekens 1994) and technical (Rierink 1995) inputs. Traditionally, demographers study net migration of countries.
