OECD Methodology - International Migration Database
Most of the data published in the OECD international migration database database are taken from the individual contributions of national correspondents appointed by the OECD Secretariat with the approval of the authorities of Member countries. Consequently, these data have not necessarily been harmonised at international level. This network of correspondents, constituting the Continuous Reporting System on Migration (SOPEMI), covers most OECD Member countries as well as the Baltic States, Bulgaria and Romania. SOPEMI has no authority to impose changes in data collection procedures. It is an observatory which, by its very nature, has to use existing statistics. However, it does play an active role in suggesting what it considers to be essential improvements in data collection and makes every effort to present consistent and well-documented statistics.
No data are presented on the native population, since the purpose of this database is to describe the “immigrant” population (generally the foreign born population). The information gathered concerns the flows and stocks of the total immigrant population and immigrant labour force, together with data on acquisition of nationality. The presentation of the series in a relatively standard format does not imply that the data have been fully standardised and are comparable at an international level, since few of the data sources used are specifically designed to record migration movements. Because of the great variety of sources used, different populations may be measured. In addition, the criteria for registering population and the conditions for granting residence permits, for example, vary across countries, which means that measurements may differ greatly even if a theoretically unique source is being used.
In addition to the problem of the comparability of statistics, there is the difficulty of the very partial coverage of illegal migrants. Part of this population can be counted through censuses. Regularisation programmes, when they exist, make it possible to account for a far from negligible fraction of illegal immigrants after the fact. In terms of measurement, this makes it possible to better evaluate the volume of the foreign population at a given time, although it is not always possible to classify these immigrants according to the year they entered the country.
Since the nature of the sources used differs considerably across countries, each series is provided with an explanatory note aimed at making it easier to understand and use the data presented.
The database provides annual series for the most recent years (in general 1990-2007).
For more information, visit the OECD website.
SEEMIG Managing Migration and its Effects in South-East Europe - Transnational Actions Towards Evidence Based Strategies
The project is funded under the 3rd call of the South East Europe Programme.
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