MP for Windsor
Working Hard For You
Accuracy of immigration statistics

Adam Afriyie (Windsor, Conservative): To ask the Minister for the Cabinet Office what assessment he has made of the accuracy of the International Passenger Survey for estimating migration flows; and if he will make a statement.

Nick Hurd (The Parliamentary Secretary, Cabinet Office; Ruislip, Northwood and Pinner, Conservative): The information requested falls within the responsibility of the UK Statistics Authority. I have asked the authority to reply.

Letter from Glen Watson

As Director General for the Office for National Statistics, I have been asked to reply to your recent Parliamentary Question asking the Secretary of State for the Home Department, what assessment she has made of the accuracy of the International Passenger Survey for estimating migration flows; and if she will make a statement.

ONS publishes estimates of long-term immigration, emigration and net migration each quarter. These are largely derived from the International Passenger Survey (IPS). The estimates are published alongside their margin of error which refers to the 95 per cent confidence interval, and is a measure of the uncertainty associated with making inferences from a sample.

The latest IPS estimate for long-term immigration for the year ending December 2013 was 485,000, with a margin of error of +/- 29,000. The latest IPS estimate for long-term emigration for the year ending December 2013 was 295,000, with a margin of error of +/- 19,000.

ONS has published an overview of the quality and reliability of the International Passenger Survey (IPS) in relation to producing estimates of long-term international migration flows, that is, flows of migrants intending to remain in or out of the UK for twelve months or more. This can be accessed at:

http://www.ons.gov.uk/ons/guide-method/method-quality/specific/population-and-migration/international-migration-methodology/international-passenger-survey-quality-information-in-relation-to-migration-flows.pdf

Furthermore, ONS has recently published a review into the ‘Quality of Long-Term International Migration Estimates from 2001 to 2011’. This review found that a substantial amount of immigration, particularly of EU8 citizens, between 2004 and 2008 was missed by the IPS, prior to improvements to the design and coverage of the survey in 2009. Revised net migration estimates, which are consistent with the results of the 2011 Census, were published as part of the review. The review can be found at:

http://www.ons.gov.uk/ons/rel/migration1/long-term-international-migration/quality-of-long-term-international-migration-estimates-from-2001-to-2011/sty-quality-of-ltim.html

The improvements to the IPS have reduced the relative error around the estimates, as well as the balance of the sample between EU and non-EU migrants.