Case 2 - Research on methods of estimating immigration to local authorities in England helped National Statistics improve their immigration and population statistics
Submitting Institution
University of LeedsUnit of Assessment
Geography, Environmental Studies and ArchaeologySummary Impact Type
PoliticalResearch Subject Area(s)
Mathematical Sciences: Statistics
Studies In Human Society: Demography
Summary of the impact
The quality of estimates in the 2000s of immigration to local authority
areas in England needed radical improvement. School of Geography (SoG)
researchers Rees and Boden developed a method, based on administrative
data including NHS Patient, National Insurance and Higher Education
records, to improve the accuracy of immigration estimates. The research
had a direct impact on the Office for National Statistics (ONS), which
adopted and further developed the method for annual estimates of local
immigration statistics. These are used as inputs to mid-year population
estimates and projections, which play an important role in formulae for
allocating funds to local authorities and health bodies.
Underpinning research
Numbered citations refer to underpinning publications, e.g. [1],
and funding, e.g. [IV].
Context of the Research
Local authority (LA) populations in England gain people from births,
in-migration and immigration, and they lose people through deaths,
out-migration and emigration. Since 2000, net international migration has
directly contributed 54% to population growth in the UK. Between the 2001
and 2011 Censuses, there was a 63% increase in the number of people living
in the UK who were born abroad. However, the official system for
estimating immigration to LAs needed radical improvement. Immigration
estimates are a key input to population estimates that are used to
allocate funds to local authorities, so accuracy is crucial.
Difficulties with using survey and census data (the pre-2011 ONS
method)
In 2006 Philip Rees (Professor) and Peter Boden (Director, Edge
Analytics Ltd, SoG PT Research Fellow 2008-11, SoG PhD 1989) were
commissioned by the Greater London Authority [I] to estimate
changes in London's immigrant population in the 2000s. This work
highlighted the need for better statistics on immigrants to UK local
areas. Prior to 2011 ONS used International Passenger Survey (IPS) data,
the Labour Force Survey (LFS) and the 2001 Census to produce sub-national
statistics on international migration at regional and local scales. The
IPS and LFS sample only a small proportion of arrivals, making regional
and local estimates unreliable. Because data from the 2001 Census were
used to allocate immigrants from intermediate zones to local areas,
sub-national estimates of immigration became problematic after 2004 when
large numbers of immigrants from Eastern Europe entered the UK.
Use of administrative data and a new model for estimating local
immigration
Rees and Boden therefore proposed a new framework, the New Migrant
Databank (NMD) [1]. The NMD is a database containing aggregate
statistics that proxy immigration from all administrative, survey and
census sources in the public domaiincluding NHS and National Insurance new
registrations by people previously resident abroad. The NMD provided
surrogate variables for local immigration which could be used in improved
models allocating national immigration totals to local areas.
Review for the UK Statistics Agency (UKSA)
Rising concerns about the accuracy of migration statistics led the UKSA
to commission [II] a review of the migration statistics literature
by a University of Leeds team [2]. The review concluded that the
ONS should adopt methods based on administrative data to improve their
estimation of immigration statistics. The Leeds researchers compared the
results of the ONS method for allocating national totals to local
authorities with a simple allocation using GP new registrations of
immigrants. This data set covered most of the target population of
immigrants whereas the ONS allocations to regional and local areas were
only based on sample surveys, the LFS and IPS.
Estimation of immigration to English local authorities by ethnicity
The Leeds work was further developed through ESRC funding awards [III]
and [IV]. For the ethnic population projections, the researchers
needed to estimate immigration to all English local authorities by ethnic
group. The model presented in [2] was refined by using different
administrative sets for each broad age/purpose of migration group. The
researchers used National Insurance Numbers issued to persons previously
resident outside the UK for those entering work aged 16-64, Higher
Education Statistics Agency data on foreign students for those coming for
study and the new GP registrations of persons previously resident abroad
for children aged 0-15 and for the retired, aged 65+ [3, 4]. This
method gave more robust results than the existing ONS method based on
survey data. In a journal paper [5], Rees and Norman
(lecturer since 2006) quantify the importance of immigration on the ethnic
group populations of the UK and local authorities.
References to the research
The commissioned reports (outputs 1 and 2) were key inputs in the
development of outputs 3, 4, and 5, which were funded by ESRC and
published in: an internationally-recognised, peer-reviewed journal which
is a flagship journal of the Royal Statistical Society (output 3); a peer
reviewed book chapter (output 4); and a peer reviewed journal of the Royal
Geographical Society (output 5). Output 3 is included in REF2.
[1] Report commissioned by the Greater London Authority (GLA), who
were concerned about official immigration estimates for London
Rees, P. and Boden, P. (2006) Estimating London's new migrant
population. A Report commissioned by the Greater London Authority for
the Mayor of London. Available at:
http://static.london.gov.uk/mayor/refugees/docs/nm-pop.pdf.
Accessed 24/9/2013.
[3] The paper setting out the alternative methodology for estimating
immigration to local authorities
Boden, P. and Rees, P. (2010). Using administrative data to
improve the estimation of immigration to local areas in England, Journal
of the Royal Statistical Society Series A - Statistics in Society,
173(4), 707-731. DOI: 10.1111/j.1467-985X.2009.00637.x. Cited by 22,
Google Scholar.
[4] A full account of the methodology in a recent book (all chapters
were peer reviewed)
Boden, P. and Rees, P. (2010) New Migrant Databank: concept and
development. Chapter 6, pp.111-132 in Stillwell, J., Duke-Williams, O. and
Dennett, A. (eds.) Technologies for Migration and Commuting Analysis.
IGI Global, Hershey, PA. Print ISBN 9781615207558, eISBN 9781615207565.
[5] Peer reviewed paper using the immigration estimates that shows
the importance of immigration in subnational population change
Rees, P., Wohland, P. and Norman, P. (2013) The demographic
drivers of future ethnic group populations for UK local areas 2001-2051, The
Geographical Journal, 179(1): 44-60. DOI:
10.1111/j.1475-4959.2012.00471.x. Open access paper
Research Funding for the underpinning research
[I] Rees and Boden, The Greater London Authority, 2005-6, Estimating
London's New Migrant Population: Review of Methodology. Consulting
Leeds, £15k. This funded output 1.
[II] Rees, Stillwell, Boden, Dennett, UK Statistics
Authority, 2009, Academic Review of Migration Statistics Literature.
Consulting Leeds, £15k. This funded output 2.
[III] Rees and Norman, ESRC RES-163-25-0032, 2007-2010, What
happens when international migrants settle? Ethnic group population
trends and projections for UK local areas under alternative scenarios.
University of Leeds, £252k (100% FEC). Graded Very Good. This funded
outputs 3 and 4.
[IV] Norman and Rees, ESRC RES-189-25-0162, 2010-11, Ethnic
group population trends and projections for UK local areas:
dissemination of innovative data inputs, model outputs, documentation
and skills. University of Leeds £106k (100% FEC). See http://www.ethpop.org/
(Accessed 24/9/2013) which disseminates the projections. This funded
output 5.
Details of the impact
The ONS produces population estimates for each mid-year (MYEs) for local
authorities. The latest MYEs form the base populations in sub-national
population projections (SNPPs). These MYEs and SNPPs are used throughout
central and local government in planning services and in allocating
resources from central to local government. For example, the SNPPs for a
funding year were used to drive the funding formula that allocated an NHS
budget of £89 billion to Primary Care Trusts in England [A]. The
ONS uses a cohort-component model to roll forward local area populations
from the 2001 Census. The immigration component is highly uncertain and
this affects MYEs directly. The research has had a direct impact on ONS,
who have adopted and further developed the Leeds approach to estimating
immigration to local authorities. To understand this impact, we first
outline how the researchers developed the new estimation model for
immigration to local authority areas, in collaboration with end users. We
then turn to the specific impacts of the research for ONS.
The process leading to impact
ONS estimates total immigration to the UK by year using the IPS with Home
Office information on Asylum seekers and Irish Central Statistical Office
data on UK-Irish Republic migration. Prior to 2011 ONS employed the IPS
and LFS to allocate the national immigration estimates to English regions
and Wales (10 zones). The IPS was utilized to distribute regional totals
to intermediate zones (63 zones). Census 2001 immigration statistics were
then used to assign intermediate zone totals to local and health
authorities. However, the GLA were sceptical that the very small IPS could
be used to estimate immigrants at the intermediate geography scale and
were concerned that use of the 2001 Census would misestimate the
distribution of new immigrants from countries which joined the EU in May
2004. In 2006 at the request of the GLA, Rees and Boden compiled
administrative data proxies for local authorities and used them to create
new estimates of sub- national immigration [1].
Impacts on the ONS methodology for the estimation of sub-national
immigration
After a commissioned evaluation [B], the ONS adopted the SoG
recommendations that sub-national immigration be estimated by allocation
the national totals by purpose of migration. ONS made improvements by
using detailed administrative data available to National Statistics. For
example, ONS used Migrant Worker Scan data (Department of Work and
Pensions) to distribute immigrants coming to work. Higher Education
Statistics Authority data were used to distribute University students from
outside the UK to subnational areas. GP Patient Register data were
employed to distribute immigrant children, dependents aged 17-59 and those
aged 60+. Home Office data were used to distribute asylum seekers. The
methodology generated the sub-national immigration estimates employed in
the 2011 local population estimates and will be used in future population
estimates and projections. Full documentation on the methodology and its
impacts was published on 17 November 2011 [C].
In an email [D] to Rees, the ONS project leader confirmed
the importance of the Leeds research:
"Work undertaken by Phil Rees and Peter Boden on using administrative
data to distribute national immigration flows to local authority level
has laid an important foundation to the improved methodology developed
by ONS. This work has been elaborated on by ONS through improved access
to a range of administrative data sources. These improved immigration
figures have been incorporated into a set of indicative population
estimates, which are widely accepted as being an improvement on the
current figures. These in turn have been used for the 2010-based
sub-national projections published on 21 March 2012, which are a key
input in allocating local authority funding from central government. ONS
intend to use this approach moving forward from the 2011 Census and so
this work will leave a lasting legacy."
Local authority planning has benefitted from the improved local
population estimates resulting from the new sub-national immigration
estimates. The GLA demographer wrote as follows [E]:
"The work that SoG carried out on improving immigration estimates has
been of immense use to us here at the GLA. Prior to the introduction of
the revised MSIP/IMPS methodology by ONS, informed by your work, we had
very little faith in the accuracy of estimates of immigration to local
authorities in London or even for the city as a whole. I consider the
approach to improving the methodology to be sound and sensible and the
subsequent estimates are shown to be far more realistic than what has
gone before by all sources of evidence that we have available to us -
most notably the results of the 2011 Census. The estimates have afforded
the opportunity to greatly improve central funding allocations within
the capital. The availability of the improved estimates for use in our
own population modelling work has been one of the biggest steps forward
in the quality of intelligence we've been able to provide to decision
makers and planners across the capital."
The Intelligence Manager of Leeds City Council, wrote to say [F]:
"the 2011 Census endorsed the work that Peter Boden had undertaken,
showing a fall [far] smaller population compared to what had previously
been suggested by ONS. The subsequent future estimates for the Leeds
population are now accepted as a more robust representation of the
changes to population for Leeds, and LCC are pleased to see that the
involvement of Peter Boden and yourself have led to the amendment of the
methodology now adopted by ONS to improve the accuracy of immigration
estimates; LCC has also accepted that the improved accuracy for the
estimates of immigration to local authority areas will negatively impact
upon the allocated funding received from central government, based upon
the revised methodology."
What the new population estimates will mean for local authorities from
2013 onwards
An ONS publication [G] compared two sets of mid-year 2011 MYEs
for LAs: (1) MYEs rolled forward from Census 2001 using old
immigration estimates, (2) MYEs rolled forward from Census 2001 using new
immigration estimates with MYEs rolled forward populations from Census
2011, the most accurate. Set (2) population estimates are much closer than
the set (1) to the Census 2011 estimates. The changes in sub-national
immigration estimates led to a revision of the 2005- 2011 MYEs and
2011-2036 projections in the 2010 based SNPPs.
The impact of switching to immigration estimates using the new
methodology has been measured in an ONS report [H], independently
verified by the Leeds researchers. The report shows significant shifts in
estimated immigration occurred from local authorities in the East of
England, Yorkshire and The Humber, South East and South West to the West
Midlands and London.
The new population estimates and projections influence the budgets of LAs
and local health agencies because they are used by central government to
allocate resources. For example, consider a thought experiment in
which £100 billion is allocated to local agencies. By using SNPP
populations employing the new immigration estimates and assuming
population to be the only driver of allocations, there would be a shift of
£1.9 billion in 2020 allocations. Some 156 LAs would see increased budgets
LAs with Newham (+£145m) and Brent (+£91m) at the top and 170 LAs would
lose with Leeds (-£99m) and Bristol (-£101m) at the bottom. Actual
allocations are, of course, more sophisticated and nuanced, because
factors other than the population are taken into account. However, the
experiment serves to demonstrate that demographic methods can potentially
influence the delivery of services to local residents in important ways.
Sources to corroborate the impact
[A] Department of Health (2011) Resource Allocation: Weighted
Capitation Formula. Seventh Edition. Pp.21 and 27. Available at:
https://www.gov.uk/government/publications/resource-allocation-weighted-capitation-formula.
Accessed 12/10/2013.
[B] Bijak, J. (2010) Independent review of methods for distributing
International Immigration Estimates to Regions. Available at: http://tinyurl.com/pdqfjke.
Accessed 24/9/2013 [Available on request]
[C] ONS (2011a) Improved Immigration Estimates to Local Authorities
in England and Wales: Overview of Methodology. Office for National
Statistics, Research Report, 17 Nov 2011. Available at:
http://www.ons.gov.uk/ons/guide-method/method-quality/imps/improvements-to-local-authority-immigration-estimates/overview-of-improved-methodology.pdf.
Accessed 24/9/2013. Section 3.2, p6 discusses the University of Leeds
approach.
[D] Email from the ONS project leader [Available on request]
[E] Email from GLA Demographer [Available on request]
[F] Email from Leeds City Council Intelligence Manager [Available on
request]
[G] ONS (2013) Comparison of Previous and Improved Methods of Estimating
International Immigration at Local Authority Level. Research Report, 26
June 2013. Available at:
http://tinyurl.com/p3w6gg2 .Accessed24/9/2013
[Available on request]
[H] ONS (2011b) Impact Assessment of Improved Immigration Estimates
on Local Authorities in England and Wales. Research Report, 17 Nov
2011. Available at:
http://www.ons.gov.uk/ons/guide-method/method-quality/imps/improvements-to-local-authority-immigration-estimates/imps-impact-assessment.pdf
Accessed 24/9/2013.