Please note that this summary has now been superseded due to the publication of the full Long-Term International Migration (LTIM) quality review. An updated summary about the Quality of Long-Term International Migration estimates from 2001 to 2011 was published on 10 April 2014.
Every 10 years the population Census provides the opportunity to compare mid-year population estimates with a count of the population at a given point in time. Population estimates are produced from administrative records on births and deaths and Long-Term International Migration (LTIM) estimates in addition to other adjustments.
The Census-based 2011 mid-year population estimate for England and Wales was 464,000 higher (0.8%) than the mid-year population estimates rolled-forward from the 2001 Census base. There are several possible causes for this small difference but it was considered that the ‘largest single cause is most likely to be underestimation of long-term immigration from central and eastern Europe in the middle part of the decade’ ( ONS, 2012 (171.1 Kb Pdf) ). This was before improvements were made to the International Passenger Survey in 2009.
In light of the results of the 2011 Census, ONS has published revised net migration figures as components of change in revised mid-year population estimates from the year ending mid-2002 to the year ending mid-2010 for the UK. Table 1 below provides an at-a-glance comparison of final LTIM estimates with the revised net migration components of the mid-year population estimates for the United Kingdom.
Table 1: Revised Net International Migration estimates for United Kingdom(1)
|Final LTIM net migration estimate||New mid-year estimate (MYE2) net migration (revised)||Difference between revised MYE2 net migration and final LTIM net migration estimate|
Table source: Office for National Statistics
- Sources: ONS, Long-Term International Migration (Table 2.10), mid year for United Kingdom ONS, Mid-year population estimates for United Kingdom
- MYE is Mid-Year Estimates
Both LTIM and the revised net migration estimates are subject to uncertainty. For more information please see the Quality and Methodology Information for LTIM estimates (329.4 Kb Pdf) , Mid-year population estimates (150.7 Kb Pdf) and Census estimates (179.3 Kb Pdf) .
In 2009, improvements were made to the IPS to make it much better focussed on migration and to increase the geographical coverage of ports of entry to the UK. For more information see International Passenger Survey: Quality Information in Relation to Migration Flows (214.2 Kb Pdf) . It is important to note that if these improvements had been made prior to 2009, then ONS would have expected the rolled-forward population estimates and the 2011 Census count to have been closer.
As shown in Table 1, the revised net migration component of change for the mid-year estimates are different from the published estimates of LTIM for United Kingdom. ONS has conducted a further review examining these differences, incorporating available data sources to assess the quality of LTIM estimates during the decade from 2001 to 2011. The initial findings of the review are:
Evidence shows that the IPS did not sufficiently identify migration of EU8 nationals between 2004 and 2008
The improvements delivered to the IPS in 2009 were successful in adequately increasing coverage and improving the accuracy of the estimates.
There is no evidence to suggest that changes in methodology are necessary to LTIM adjustments.
Analysis of 2011 Census data on ‘address one year ago’ showed that LTIM estimates were lower for immigration flows for EU-born people but were higher for immigration flows for non-EU born people
Some evidence suggests that the IPS may not adequately identify migrant children aged under 15. Further investigation is planned for 2014 and will continue until e-Borders data are available to compare immigration flows with the IPS for this age group.
The full review will be published in spring 2014.