Answers to frequently asked questions about migration and population projections
- What is the definition of a long-term international migrant?
- Are short-term migrants included in the projections?
- Are the projections based on reliable migration data?
- What about illegal migration and those who overstay?
- How has migration from Eastern Europe affected projections?
Projections use the United Nations definition of an international long-term migrant, where a long-term international migrant is a person who moves to a country other than that of his or her usual residence for a period of at least 12 months, so that the country of destination effectively becomes his or her new country of usual residence. From the perspective of the country of departure the person will be a long-term emigrant, and from that of the country of arrival the person will be a long-term immigrant.
Short-term migrants do not fall under the United Nations definition of usually resident population used in population estimates and projections, and as such short-term migrants are excluded from the population. ONS publishes estimates of short-term migrants at national and subnational level. The subnational estimates of short-term migrants are currently classified as experimental statistics.
The projections are based on the most up to date migration estimates available at the time they are produced, but it is recognised that migration is one of the most difficult components of population change to measure accurately. There is no single, comprehensive source of data which can provide the information at national and/or local levels.
ONS recently led a cross-government Migration Statistics Improvement Programme (MSIP) to improve estimates of both internal and international migrants. Improvements from Phase 1 of the MSIP were introduced in May 2010 resulting in the population estimates for 2002 to 2008 being revised using new methods. Phase 2 of the MSIP has subsequently produced indicative results for the 2006 to 2010 estimates including increased use of administrative data sources to distribute estimates of international immigrants to local authority level. The improved migration estimates have incorporated feedback from users, and have been subject to extensive quality assurance. Further information on all aspects of the MSIP is available on the website.
The international migration estimates upon which the migration assumptions are based do not explicitly include estimates of the number of people entering or staying on in the UK illegally. However:
they include estimates of the number of people claiming asylum and remaining in the country for more than 12 months. Hence, overstaying asylum seekers are implicitly included in the estimates. Allowance is made for those who depart voluntarily, and also for removals
the IPS is based on stated intentions of survey contacts, not on actual visa or immigration status. People entering legally on a visitor visa but who subsequently overstay and remain in the country for more than 12 months may be included in the international migration estimates as either long-term migrants or visitor switchers. Their inclusion in international migration estimates is dependent on their response to the intended length of stay question in the IPS on arrival to or exit from the country
anyone who enters the UK clandestinely and does not go on to apply for asylum will not be included in estimates of international migration