Most of the data published in this annex have been provided by national correspondents of the continuous reporting system on migration appointed by the OECD Secretariat with the approval of the authorities of Member countries. Consequently, these data are not necessarily based on common definitions. Countries under review in this annex are OECD countries for which data are available, as well as the Russian Federation. The continuous reporting system on migration 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.