Population Estimates and Projections and Migration Statistics
User Requirements Report
This Report was prepared in 2010 and covers user requirements for population estimates and
projections and migration statistics published by the Population and Demography Division
(PDD) (formerly titled ONS Centre for Demography or ONSCD) within ONS. Inevitably,
some aspects of outputs and known requirements have changed since this report was
prepared. Some changes have been reflected in the main body of the text while other changes
are noted in the text within square brackets. A revised version of the report will be published
in 2012.
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1. Introduction and background
1.1 The ONS Centre for Demography (ONSCD) publishes a broad range of population and
migration related outputs from the well established mid-year population estimates (MYEs) to
relatively new outputs such as estimates of the number of short-term migrants in England &
Wales. It is important to ensure that these outputs continue to meet user requirements and
needs in terms of relevance, timeliness, accuracy, coherence and quality. This report provides
a summary of the current user requirements for population and migration outputs produced by
ONSCD. It identifies who the key users are, describes what information sources have been
used to identify user requirements, and discuss the identified user requirements.
1.2 A full user consultation exercise was not considered appropriate for this purpose for this
purpose for two reasons. Firstly, a number of other consultations have recently taken place
related to the Migration Statistics Improvement (MSI) work programme and an additional
consultation in close proximity to these would create additional burden for users.
Furthermore, the UK Statistics Authority will be undertaking assessments of all the division’s
outputs in the near future which will require significant user involvement; a separate ONSCD
consultation taking place now may cause confusion to users. [Assessment of most of these
outputs has now been completed and assessment reports are available on the UKSA website].
1.3 In the absence of a consultation, information has been collected from a number of internal
sources from within the division. These include information from responses to related
consultations, branch-specific knowledge about users and their requirements, information
from meetings of user engagements groups (such as the CLIP Population Sub-Group) and
correspondence between users and the division. Details of these response-to-consultation
papers used are provided in Appendix 1.
2. Current outputs produced by ONSCD
ONSCD produces and publishes a range of population and migration outputs on a regular
basis which can be grouped into three broad categories; population estimates, population
projections and migration statistics. Within these categories the individual outputs are:
Population Estimates
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National and local authority mid-year estimates (MYEs)
Small area population estimates (middle and lower super output areas)
Population estimates for other areas (parliamentary constituencies, wards, primary care
organisations and national parks)
Marital status population estimates
Population estimates of the very elderly
Population estimates by ethnic group
Household population estimates
Electoral statistics
2
Population Projections


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National population projections for the UK and constituent countries
Sub-national population projections for England.
Marital status population projections for England and Wales.
Migration Statistics
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Long-term international migration estimates
Short-term international migration estimates
Internal migration estimates
Population estimates by country of birth and nationality
Migration indicators for local areas
3. User information and requirements
This section discusses each broad output category in turn. Consideration is given to the main
users are, what the outputs are used for and what the main user requirements are. Where
applicable, suggestions for improvements and / or changes to outputs provided by users are
also presented.
3.1 User requirements for Population Estimates
3.1.1 Population estimates describe the sex and age structure of the population of the UK, its
constituent countries and sub-national areas for intercensal years. The benchmark population
estimates are the annual mid-year population estimates (MYEs) which show the number of
usually resident people in the UK, its constituent countries and local authority districts as at
30th June each year. They are now produced with a time lag of approximately twelve months
so estimates for mid-2008, say, are published in June 2009. In addition to the MYEs, a suite
of other population estimates outputs are produced for different population groups; these are
listed in section 2 above.
3.1.2 Population estimates have a wide range of users and are used for a variety of purposes,
as summarised in table 1 below.
Table 1: Population estimates outputs – users and uses
Output
Main users
Output used for
National and local
authority mid-year
population estimates


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Central Government
(CLG)
Local authorities

Academics and research
bodies
3
Resource allocation
Planning and monitoring of
services
Derivation of grossing factors
for surveys, and denominators
in the calculation of rates



Businesses and
commercial companies
Central Government
(ONS)

Understanding demographic
characteristics of an area
Base for national and
subnational population
projections
Small area population

estimates (middle and
lower super output areas)
Local authorities

Denominators for rates,
calculation of indices of
deprivation, service & resource
planning and as a base for local
level projections by LA
Population estimates for
other areas
(parliamentary
constituencies, wards,
primary care
organisations and
national parks)

Local authorities

Denominators for rates,
calculation of indices of
deprivation, service & resource
planning and as a base for local
level projections by LA
Marital status population
estimates

Central Government
(ONS)

Input data for marital status
population projections and
calculations of marriage rates
Population estimates of
the very elderly

Central Government
(ONS)


Academics / researchers

Calculation of age-specific
mortality rates for use in
producing life tables and
national population projections
Research projects related to the
older population

Local authorities


Academics / researchers

Household population
estimates

Central Government
(ONS and others)

Grossing of household surveys
such as the LFS
Electoral statistics

ONS Boundary
Commission


Central Government
(ONS)

Reviewing and developing
parliamentary constituency
boundaries
Answering Parliamentary
Questions and for research
purposes as an administrative
data source
Population estimates by
ethnic group
4
Planning and monitoring of
services for ethnic groups,
calculation of rates by ethnic
group
Research projects and studies
where population by ethnic
group is required
3.1.3 Users generally feel that the population estimates outputs produced by ONSCD do
meet their requirements as shown by feedback received from consultations, user group
meetings and direct feedback provided by users to ONSCD. In addition, users are generally
supportive of the work ONS is doing to improve population estimates outputs in terms of
range, quality and timeliness. However there are some areas where users have commented
that requirements could be better met and users have suggested areas for improvement. These
are discussed below. In particular, Eurostat (the statistical office of the European Union) has
raised concerns that their requirements for UK demographic statistics are not being fully met.
These are discussed below.
3.1.4 Analysis of the information sources described in section 1.4 has identified a number of
user requirements from ONSCD’s population estimates outputs. These user requirements can
be grouped into four broad categories:
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Mid-year population estimates by local authority (LA)
Population estimates at small area level
New outputs and products
Eurostat requirements
3.1.5 Mid-year population estimates for the UK and LAs by age and sex are a key
requirement for the users of population estimates, who require up-to-date information on the
sex and age structure of the population. These include central and local government and they
require accurate and high quality population estimates at local authority level for allocating
government funding and planning of services for local areas. MYEs are produced annually
by ONS using a well established demographic approach, the cohort component method, and
using data sources which are the best that are available on a nationally consistent basis down
to local authority level. Users recognise the MYEs as the official population estimates for the
UK, constituent countries and local authorities and feedback has shown it meet many of their
requirements. However, users have commented on additional requirements for these
population estimates including:

Extending the age range to age 99 and 100 and above
At present, MYEs are produced to age 89 and age 90 and above at both national and
local authority level. They are not produced at single year of age for the older ages
mainly due to misreporting of age information for these older ages in the Census.
ONS however does produce Population Estimates for the Very Elderly by single year
of age and sex for ages 90 to 104, and 105 and above. However, these are produced
using a different method to that of MYEs and do not hold the National Statistics
quality status as the MYEs.

Improved timeliness of release of population estimates
Traditionally, MYEs have been produced with a time lag of approximately fourteen
months after the reference date, so that population estimates for mid-2008 for
example, would be published in August 2009. The time lag reflects the availability of
the data sources which measure the components of population change and the time
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required to process data and produce the estimates. Users would like to see population
estimates available as soon as possible after the reference date. ONS is concerned to
improve timeliness; the mid-2009 estimates (published in 2010) are the first to be
published in June, a reduction of the time lag by two months, and future estimates will
be published within a year of the reference date.

Population estimates for local authorities by age, sex and ethnic group
There has been an increasing and significant interest in the availability of up-to-date
estimates of the population of ethnic groups for by local authority. The Census
provides detailed information on population by ethnic group but estimates for years in
between censuses has relied on information from household surveys which are
restricted to high level of aggregation of geography or ethnic group. While some local
authorities have produced estimates for their own areas, there has been no consistent
set of detailed set of estimates by age and sex for all local authorities in England and
Wales. Since 2006, ONS has produced population estimates by age, sex and ethnic
group for all local authorities in England using a similar methodology used to produce
the MYEs.
3.1.6 There continues to be a strong user demand for small area population statistics as
evidenced by feedback to a number of user consultations and user engagement groups. Local
authorities are important users of small area population statistics and use small area
population estimates for a range of purposes including as a base for population projections
and forecasts, planning and monitoring of services, and as denominators for the calculation of
rates for other statistics. In response to user demand ONS first produced ward level
population estimates in 2005 and a parallel consultation showed strong demand for these
statistics. Following this, ONSCD has produced population estimates for Middle Layer Super
Output (MSOA) areas and also Lower Layer Super Output (LSOA) areas. In addition to ward
and SOA estimates users have reported their requirements for other small areas. These
include

Population estimates by National Parks, Parliamentary Constituency and PCO areas
New geographic areas or groupings may develop for a number of reasons such as the
result of administrative changes or the introduction of a new government initiative or
policy. It therefore becomes important for users to have reliable population statistics
for these new areas. ONSCD has developed a ‘Post Code Best Fit’ methodology to
derive estimates for other geographies from the LSOA estimates. ONSCD now
produce estimates for National Parks, Parliamentary Constituencies and Primary Care
Organisations using this method. In addition, bespoke population estimates for other
small areas can also be provided, where these areas can be readily defined
geographically e.g. parishes.

Additional age detail
A common theme amongst users has been the need for more detailed age breakdown
for small area population estimates, in particular at LSOA level. LSOA estimates are
published by broad age-group and sex and users have expressed more age detail such
as quinary age-groups and single years of age. Whilst ONS is not intending to publish
LSOA estimates with a more detailed age breakdown, requests for different age detail
to that published may be made available on request.
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3.1.7 Some users have indicated the need for new outputs or variations of existing outputs.
ONSCD has responded by undertaking research and, where feasible and appropriate, has
produced these to meet user requirements. These include

Population Estimates by Ethnic Group (PEEGs) for Primary Care Organisation
(PCO) areas, local authorities in Wales, and for wards
Following the first publication of PEEGs in 2006 there has been demand for other
related products to enable more effective planning and monitoring of services for
ethnic groups. User requirements have included new estimates for local authorities in
Wales (PEEGs were first produced for local authorities in England only) and also
PCO areas in England. ONS now produce PEEGs for all local authorities in England
and Wales and by PCO areas in England. Other users have expressed a need for these
estimates at lower geographic areas, specifically at ward level.

Population estimates on different bases
In an increasing complex and mobile society there is a need for population estimates
to be produced on a more flexible basis. Different users of population estimates may
require population statistics on different bases, such as where people usually live
(‘usual residence’) or where they are on a particular day (‘population present’). Midyear population estimates are currently produced on the usual residence definition of
the population. An ONS consultation on future population bases revealed that users
support the usual residence definition of the main population base but that they also
require estimates of the population on different bases such as those living in private
households and communal establishments. In addition local authority users expressed
a requirement for visitor information to be collected in the 2011 Census which would
enable population estimates to be made on a ‘usual residents plus visitors’ base. This
would reflect more closely the number of people using services in an area, including
visitors.
3.1.8 Eurostat is an important user and customer of population and migration statistics
produced by ONSCD. Each year Eurostat requests demographic statistics form all EU
member states including the UK through a number of data collections. It should be noted that
Eurostat require all population data as at 1 January each year and not mid-year. Eurostat
require the following population data:
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Population of the UK by single year of age and sex
Population of the UK by single year of age, sex and marital status
Population of the UK by single year of age, sex and educational attainment
Population of the UK by single year of age, sex and urban / rural residence
Population by single year of age, sex and NUTS2 area in the UK
Population by broad age-group, sex and NUTS3 area in the UK
Population density by NUTS3 area in the UK
ONSCD provide a range of a population statistics to Eurostat in the form of tabular datasets.
The datasets listed above are collected through the Eurostat’s Demographic Data Collection.
Where required, for example to compile UK level statistics, data are also provided by the
National Records of Scotland (NRS) and the Northern Ireland Statistics and Research Agency
(NISRA) which ONSCD use to compile UK level estimates.
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Statistics collected through the Demographic Data collection (including the above datasets)
are all voluntary at present. Therefore ONS is not legally required to provide these statistics
if they are not able to do so. However there are a number of important uses of these data and
ONS strives to provide as much of these statistics wherever possible. Due to the voluntary
status of this data collection and the increasing importance of having comprehensive
demographic statistics for all EU member states, Eurostat are in the process of introducing a
new regulation to formalise the future collection of population statistics. The introduction of
a regulation is likely to mean that the supply of these statistics becomes mandatory.

Population of the UK by single year of age and sex
This requirement can be met. Although the ONS population estimates are as at midyear, 1st January estimates are produced using a combining and averaging two set of
mid-year estimates or projections.

Population of the UK by single year of age, sex and marital status
This requirement cannot be met at present because NISRA do not produce estimates
of their population by marital status.

Population of the UK by single year of age, sex and educational attainment:
This requirement cannot be met at present as ONS population estimates are not
disaggregated by educational attainment. It may be possible to derive such estimates
using survey data however, and this will require new development work.

Population of the UK by single year of age, sex and urban / rural residence
This requirement cannot be met at present as ONS population estimates are not
disaggregated by area are of urban and rural residence.

Population by single year of age, sex and NUTS2 area in the UK:
This requirement can be met. Although the ONS population estimates are as at midyear, 1st January estimates are produced by averaging two set of mid-year estimates or
projections for each NUTS2 area in the constituent countries of the UK.

Population by broad age-group, sex and NUTS3 area in the UK:
This requirement can be met. Although the ONS population estimates are as at midyear, 1st January estimates are produced by averaging two set of mid-year estimates or
projections for each NUTS3 area in the constituent countries of the UK.

Population density by NUTS3 area in the UK:
This requirement can be met.
For those requirements which are not met at present, it is expected that development work
will be undertaken to assess if the requirements can be met in the future by using new data
sources and / or methods. If the new regulation for collecting demographic statistics is
implemented by the EU, which Eurostat expects will happen, it is likely that some or all of
these data requirements will become mandatory for all EU countries. Details of which
datasets will become mandatory are not known at present.
3.2 User requirements for Population Projections
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3.2.1 While population estimates provide important information about the size of the current
population, it is equally important to understand the size, age and sex structure of the
population in future years. This is important not only at national level, but also at sub-national
level. At national level, information about the future population is a vital factor in national
planning and policy-making – for example, housing provision and pensions. At sub-national
level, future changes in the population will affect local authority resource allocation and
planning policies of local authorities, and will also feed into the planning of future healthcare
provision.
ONS produce national population projections for the UK and constituent countries. Subnational population projections for local authority areas are produced by the respective
statistical office for each constituent country – ONS, NRS, NISRA and the Welsh
Government (WAG). In addition, ONS produce projections for other administrative areas in
England such as primary care organisations. ONS also produce projections by marital status
for England and Wales.
Both national and local authority population projections are based on the latest available
MYE and a set of demographic assumptions about future fertility, mortality and migration
based on analysis of past trends and expert advice. They are produced using the
internationally accepted cohort component methodology. This method accounts for changes
which increase or decrease the population (births, deaths and net migration) and models the
effect of these changes and the passage of time on the age structure of the population.
3.2.2 Population projections have a wide range of users and are used for a variety of
purposes, as summarised in the table 2 below.
Table 2: Population projections – users and uses
Output
Key users
Output used for
National population
projections (UK and
constituent countries)

Central Government
(HMT/OBR)
Central Government
(DWP)

Central Government
(DCSF)
Central Government
(ONS)
Central Government
(CLG)


Central Government
(CLG)


Central Government




Sub-national population
projections (LA and PCO
areas in England)
9



Input into long-term fiscal
projections
Forecasting expenditure for
benefits and pensions, input
into policy analysis such as
extending working lives
programme
Basis for projecting future
school pupil numbers
Control figures for subnational population
projections
Base for household
projections
Input into resource
allocation process,
production of household
projections and policy
development

Marital status projections
(DH)
Local authorities



Academic / researchers
/ commercial
companies


Central Government
(CLG)


Central Government
(DWP)

Resource planning and
future healthcare provision
Local level planning and
monitoring of services such
as education, housing,
healthcare and social
services. Also provide basis
for LA household
projections
Various research needs
Input into production of
number and type of
households in England
Costing of aspects of future
social security requirements
3.2.3 Users generally feel that the population projections outputs produced by ONSCD do
meet their requirements as shown by feedback received from consultations, user group
meetings and direct feedback provided by users to ONS. In addition, users are generally
supportive of the work ONS is doing to improve population projections outputs in terms of
range, quality and timeliness. There are however some areas where users have commented
that requirements could be better met and have suggested areas for improvement. These are
discussed below.
3.2.4 Analysis of the information sources described in section 1.4 has identified a number of
user requirements from ONSCD’s population projections outputs. These user requirements
can be grouped into three broad categories:



Population projections for the UK, constituent countries and local authorities
Population projections variants
New outputs and products
3.2.5 Population projections for the UK, constituent countries, and local authorities by age
and sex are a key requirement for the users of population statistics, who require accurate and
high quality statistics on the future sex and age structure of the population. Users of national
population projections include central government who use these projections to forecast
future pension requirements and benefits expenditure. Local authority projections are used by
central and local government for future resource planning and healthcare provision. Users
recognise the ONS population projections as the official projections for the UK, constituent
countries and local authorities and feedback has shown these meet many of their
requirements. However, users have commented on additional requirements. These include:

Extending the age range of sub-national projections
A number of users have requested that the age range of local authority sub-national
projections be extended to show single year of age detail to age 99, and 100 and
above. At present sub-national projections are produced to age 89, and 90 and above.
This is a consequence of the base population (the mid-year estimates) on which the
projections are based, which are only produced to age 89, and 90 and above. A
10
similar user requirement for extending the age range has been identified for the midyear estimates also. National population projections however are produced by single
year of age to age 99, and 100 and above.

Improved timeliness of release of the projections
National population projections are typically published eighteen months after the base
year they are projected from, and sub-national projections typically follow six months
after the national projections. Some users have expressed a requirement for
population projections to be produced closer to the base year, whilst publishing
national and sub-national projections at the same time. The time lag from the base
year reflects the availability of the data sources which measure the components of
population change and the time required to process data and produce the projections.
The numbers of areas projected for at sub-national level means that processing time is
necessarily longer, and in addition, sub-national projections for England are
constrained to the national projections for England. This will mean that sub-national
projections will follow after the national projections. However, ONS is concerned to
improve timeliness and the projections are available in good time for the key user of
the data (CLG) for use in their resource allocation round. The timetable for the
production of the projections is not dissimilar to the timetables used in other countries.

Projections which take into account government and local policy changes
Users, in particular local authority users, have consistently expressed a need for
projections which take into account the impact of future national and local policies
affecting the population. Their main concern is that population projections are a key
component of CLG’s funding allocation process; however the projections do not take
account of the impact of government policy on population change. If the projections
were policy based this would enable better allocation of resources and planning of
services based on projections which more accurately they reflect the future
demographic situation on the ground. The population projections produced by ONS
are not forecasts and do not attempt to predict the impact that future government
policies, changing economic circumstances or other factors such as the likely housing
developments in an area might have on demographic behaviour. They simply provide
the population levels and age structure that would result if the underlying assumptions
about future fertility, mortality and migration were to be realised. Due to the
substantial technical and methodological issues that need to be overcome in order to
produce population forecasts, there are no plans to take forward this work in the short
term.
3.2.6 Projections are uncertain and becoming increasingly so the further they are carried
forward in time. It is vital that users of population projections, especially those with long-term
planning horizons, take account of this uncertainty in their planning. In addition to the
principal (or central) projection, variant projections are also published for national population
projections, based on alternative, but still plausible, assumptions. These variant projections
provide an indication of uncertainty by allowing users to consider the impact upon the
population if future fertility, mortality and migration differ from the assumptions made for the
principal projection.

Additional National Population Projection variants
11
During the consultation phase of the 2008-based national projections (where ONS,
NRS, NISRA and WAG consult with other government departments and other users)
requests were made for additional variants to be produced for national population
projections. In response to this user need, ONS have published variant projections for
the 2008-based round of projections for ‘medium high’ and ‘medium low’ mortality
assumptions, amongst others.

Subnational Population Projection variants
Users have also indicated a strong requirement for variant projections at the subnational level (not currently produced), in response to a recent consultation on subnational population projections variants. The consultation also showed there is strong
demand for housing based variants where the projections are constrained to future
levels of house building within local authorities. ONS intends to include the
production of sub-national variants in its future work plan but development work will
be subject to available resources. The variants are likely to be high and low
fertility/mortality assumption variants, high and low migration and zero net migration
assumptions. Production of housing constrained variants is likely to require
significantly more resource than the ‘standard’ variants and therefore there are not
plans to take this work forward at present.
3.2.7 Some users have indicated the need for new outputs or variations of existing outputs,
and ONSCD has responded by undertaking research and, where feasible and appropriate, has
developed these to meet user needs. These include:

Population Projections by Ethnic Group
There has been some demand from users that ONS should produce population
projections by ethnic group also, to enable more effective planning and monitoring of
future services for ethnic groups. A number of individual local authorities produce
projections by ethnic group for their own areas, and the University of Leeds has
undertaken a study looking at population projections by ethnic group. The result of
this work is due to be reported later in 2010. [This work has been published by the
University of Leeds].

Changes to Marital Status Population Projections
The latest marital status population projections are 2008 based, however these are not
produced with the same regularity as national and sub-national population projections.
They are demand based and the need for a new set is ascertained before it is produced.
The Department for Work and Pensions (DWP) have expressed a need for marital
status projections for Great Britain (rather than just England & Wales as at present).
DWP would also like to see projections which cover same sex couples and projections
for 75 years ahead. At present, the data available on the number of same-sex couples
in not reliable enough at the level of detail required by the current methodology to
produce projections for same sex couples also. Should this change in the future, it
may be possible produce projections which include same sex couples also. The latest
projections for England & Wales are produced up to 25 years ahead. ONS do not feel
that marital status projection for 75 years ahead would be fit for purpose.
3.3 User requirements for Migration Statistics
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3.3.1 Migration is an important driver of population change at both national and local level,
and it is also the most difficult component of population change to estimate. Migration can
refer to international migration (that is movement of people to / from outside the UK) and
internal migration (moves within the UK). In recent years there has been substantial change
in the size and nature of migration in the UK; it is therefore important to users that estimates
of migration are as accurate and timely as possible. Migration statistics are an important
component of population estimates and projections, which themselves underpin decision
making on policy development, resource allocation and service delivery at national and local
level. ONSCD produce a number of migration outputs; these are:

Long-term international migration estimates (LTIM) - these relate to the number of
people who enter or leave the UK for at least twelve months. These are based on
International Passenger Survey (IPS) data.

Short-term migration estimates (STM) – these relate to the number of people who
enter or leave England and Wales for more than one month but less than twelve
months. These are also based on IPS data.

Internal migration estimates - these relate to moves within the UK into and out of local
authority areas.

Population estimates by nationality and country of birth – these relate to the number of
people resident in the UK by nationality and country of birth i.e. ‘stock’ estimates of
migrants rather than ‘flows’ as for the above three outputs. These are based on
Annual Population Survey (APS) data.

Local area migration indicators – this presents a number of different indicators of
international migration such as local population by nationality, country of birth,
internal migration estimates mentioned above and also administrative data such as
National Insurance Numbers (NINO) and 'Flag 4s' which indicate that somebody
registering with a GP has a previous address outside the UK.
3.3.2 Migration statistics have a wide range of users and are used for a variety of purposes.
These are summarised in table 3 below.
Table 3: Migration Statistics – users and uses
Output
Long-term international
migration estimates
Key users
 Bank of England


Central Government
(HO and HMT)
Central Government
(ONS)
Media

Eurostat

13
Output used for
 Setting of monetary policy in
relation to supply and demand
in the economy
 Various aspect of migration
modelling work
 Component of population
estimates and projections
 Media reporting of migration
and related issues
 As overleaf
Short-term international
migration estimates
Internal migration
estimates
Population estimates by
country of birth and
nationality
Migration indicators for
local areas

Bank of England


Local authorities


Central Government
(DfES and CLG)




Central Government
(ONS)
Local authorities

Eurostat


Local authorities


Bank of England


Academics and other
demographic data users


Policy development and
understanding of the labour
market
Counts of all migrants in local
areas as short-term migrants
are not included in the MYEs
Possible use in migration
modelling work
Component of population
estimates and projections
Research purposes, and
understanding the pattern of
migration into and out of local
areas
Eurostat publications and
migration related analysis
across EU states
Better understanding of
demographic characteristics
of local areas and research
purposes
Financial planning and
forecasting
Input into various research
studies which require these
statistics
3.3.3 Users generally feel that the migration outputs produced by ONSCD some but not all of
their requirements as shown by feedback received from consultations, user group meetings
and direct feedback provided by users to ONS. In addition, users are generally supportive of
the work ONS is doing to improve statistics in terms of range, quality and timeliness through
the cross-government Migration Statistics Improvement (MSI) work programme. However
there are some areas where users have commented that requirements could be better met and
have suggested areas for improvement. In particular, Eurostat have raised concerns that their
requirements for UK migration statistics are not being met. These are discussed below.
3.3.4 Analysis of the information sources described in section 1.4 has identified a number of
user requirements from ONSCD’s migration statistics outputs. These user requirements can
be grouped into four broad categories:

Long-term international migration estimates
14



Short-term migration estimates
Internal migration estimates
Eurostat requirements
3.3.5 Long-term international migration statistics estimate the flows and characteristics of
migrants to and from the UK who move for at least a period of one year. These statistics are
used widely by government, academia, special interest groups, the media, and the general
public. International migration is also a key component of population change and is used in
the production of population estimates and projections. Users recognise that measuring
international migration is difficult because the quality and range of data sources is limited –
the UK has no single all inclusive system for measuring international migration. Estimates of
international migration are based mainly on the IPS which is subject to sampling error, and
the number of migrant contacts each year is relatively small. Whilst recognising the
difficulties of estimating international migration, users have highlighted that the ONS
international migration estimates are not fit for all the purposes they are currently used.
Furthermore, users have commented on additional requirements for these estimates. These
include:

More timely long-term international migration estimates
LTIM estimates are initially published in a First Release in the November that follows
the latest reference year i.e. there is an eleven month time lag. This reflects the
availability of the data sources required to compile the LTIM estimates (such as
additional Home Office data on asylum seekers and Irish Central Statistics Office data
on Irish flows) and the time required to process data and produce the estimates. Users
would like to see LTIM estimates available as close as possible to the reference date.
ONS is concerned to improve the timeliness of international migration estimates, and
in response to users needs, now produces provisional IPS estimates of long-term
international migration each quarter as part of the Migration Statistics Quarterly
Report (MSQR). These estimates are less comprehensive than the LTIM figures as
they exclude the other adjustments such as asylum seekers, migration between the
Republic of Ireland and the UK, and visitor and migrant switchers, but show an early
indication of how international migration is changing. This improvement has been
welcomed by users. In addition, the Home Office would like these quarterly figures to
LTIM estimates rather than IPS estimates. ONS has investigated the feasibility of
this, and starting from the August 2010 release, the MSQR will show provisional
LTIM estimates supported by provisional IPS estimates. For each quarter, since
August 2010 ONS has produced provisional LTIM estimates on a rolling annual basis.

Coherence amongst different sources on international migration statistics
International migration users are looking for coherence across different sources of
international migration statistics. This includes a number of administrative data
sources which users often quote as providing alternative estimates of international
migration at national and local level. However, these sources are not specifically
designed to measure migration international migration. A reconciliation exercise has
been carried out which compares three key administrative sources (patient
registrations, national insurance number allocations, and the worker registration
scheme) with IPS-based estimates of both long and short-term international migration.

More detailed breakdown of the estimates
15
International migration estimates are published for the UK and its constituent
countries, with some information also published for regions in England. These
estimates can be broken down further by migrant characteristics such as age, sex,
citizenship and reason for visit. Users would like to see more detailed breakdown of
the estimates by smaller geographic areas (such as local authorities) and crosstabulations with more than one migrant characteristic. However international
migration estimates are based on a small number of IPS interviews, and the estimates
can only be disaggregated to a certain level before being subject to unacceptable
margins of error. Therefore, it is often necessary to group data or aggregate to higher
geographies to reduce margins of error. Migration estimates are generally regarded as
unreliable if the standard error is greater than 25 per cent of the estimate.

More use of administrative data sources
A common theme which has emerged from consultations and user engagement
initiatives is that users of international migration statistics would like to see greater
use of administrative data to quality assure and compare with ONS estimates of
international migration. ONSCD is further utilising administrative data where
appropriate. For example, Higher Education Statistics Authority (HESA) data on
university students and the Department of Work and Pensions (DWP) Migrant Scan
data on National Insurance Number (NINo) allocations to overseas nationals are used
in the new improved methods for migration estimates at local area level. The next
phase of the MSI work programme will include a reconciliation exercise between
ONS estimates of international migration and population against various
administrative data sources.
3.3.6 Short-term migration estimates measure people entering or leaving the country (England
& Wales) for more than one month but less than twelve months. Estimates of short-term
migrants are important in order to give a more complete picture of migration into and out of
England & Wales. They also allow more direct comparisons to be made between ONS
migration statistics and counts of migrants taken from administrative sources which are
known to include both long and short-term migrants. Users have expressed a strong
requirement for estimates of short-term migration, and ONS has developed and published
England & Wales level estimates of short-term migration as experimental statistics [these
were confirmed as National Statistics in November 2011]. Users have also stated additional
requirements:




Different definitions of short-term migrants in terms of length of stay and reason for
visit
Flow and stock estimates
LA level estimates of short-term migrants
Inclusion of short-term migration estimates in the mid-year population estimates
In response, ONS has further produced a range of estimates including flows and stock figures
and by different definitions. Following development work, an initial set of LA level shortterm migration estimates for the year to mid-2007 were published as part of a research report
in October 2009.
The mid-year population estimates do not include short-term migrants as the estimates relate
to the usually resident population of an area. Usual residence is the standard UN definition
16
for population estimates and includes people who reside in the area for a period of at least 12
months. Therefore only long-term international migrants are included.
3.3.7 Internal migration estimates measure moves within the UK and ONS produces estimates
of internal migration at the country level, regions, local authorities and former health
authority level for England and Wales. These estimates currently represent the best available
source of information on movements within the UK. Because there is no single system to
record population moves in the UK, internal migration estimates are derived from two proxy
sources – the National Health Service Central Register (NHSCR) and the Patient Register
Data System (PRDS). Users of internal migration estimates are primarily in local government
and the devolved administrations. The estimates also feed into the production of population
estimates and projections for sub-national areas. Feedback has shown the estimates meet
many of their requirements. However, users have also commented on additional
requirements. These include:




More frequent internal migration estimates at local authority level
Estimates for other geographic areas such as MSOA, ward and urban / rural split
Dissemination of unrounded internal migration estimates
Disaggregation by other variables such as ethnicity and or nationality
3.3.8 Eurostat is an important user of population and migration statistics produced by ONS.
Each year Eurostat requests a range of demographic statistics from all EU member states
including the UK through a number of separate data collection exercises. The majority of
international migration statistics required by Eurostat are required under a specific European
Commission regulation and are therefore mandatory. Internal migration statistics are currently
not covered by a regulation although it is expected to be in the future. Eurostat have raised
concerns that ONS migration statistics are insufficiently reliable at the level of detail required.
ONSCD is currently investigating ways in which UK migration statistics can be brought into
line with EU requirements.
The international migration statistics required by Eurostat are specified by EU regulation
(specifically Article 3 of Regulation 862/2007) and it is therefore mandatory for all member
states including the UK to provide these statistics. Internal migration statistics however are
not included in this (or another) regulation and provision is therefore voluntary.
International migration
Eurostat require the following international migration statistics:






International immigration to UK by
o Groups of citizenship, age and sex
o Groups of country of births, age and sex
o Groups of country of previous usual residence, age and sex
International emigration from UK by groups of citizenship
International emigration from UK by age
International emigration from UK by sex
International emigration from UK by groups of countries of next usual residence
Population by citizenship, age and sex (UK)
17


Population by country of birth, age and sex (UK)
May request new data in future at NUTS2 and NUTS3 level
Eurostat Regulation 862/2007 came into effect for international migration data relating to
2008 onwards. ONSCD has since supplied data under the Regulation relating to reference
year 2008 in February 2010. However, due to the methods by which ONS produce
international migration estimates, and the detail required by Eurostat there are aspects of the
Regulation that ONSCD will not be in a position to meet due to poor data quality. A project
has been established to take forward the necessary work to identify where ONSCD will be
unable to comply with the Regulation, to develop methods that will improve the quality of the
detailed data required, and to plan and implement these improved methods.
There are two strands to the project – one dealing with migration flows, the other with
migrant stocks. Research into improving the quality of detailed data for migrant stocks is
progressing successfully, however work to date on migration flows has not proved to be
viable, and further work is currently on hold due to limited availability of resources.
[Methods have been developed to provide model-based estimates of migration flows that meet
Eurostat requirements. These were provided in September 2011 and were accepted by
Eurostat, although we are working on some additional minor improvements for 2011
migration data collection, due in Dec 2011].
Internal migration
Eurostat require the following internal migration statistics:



Internal migration by region of origin and destination (NUTS2 areas in UK)
Internal migration arrivals by sex and year of birth of migrant (NUTS2 areas in UK)
Internal migration departures by sex and year of birth of migrant (NUTS2 areas in UK)
At present, ONS is unable to meet these requirements for internal migration data at NUTS2
level. This is due to separate approaches for internal migration estimation for England &
Wales, Scotland and Northern Ireland and limitations of the data sources. Eurostat also
require calendar year data whereas ONS internal migration estimates are for mid-year to midyear.
ONS has undertaking development work to ensure these requirements are met in the future.
This work has led to the production of test data for 2001-2007 calendar year internal
migration estimates by NUTS2 areas in the UK. The test data has been quality assured with
alternative estimates produced by the University of Leeds and the two have been found to be
broadly comparable.
18
Appendix 1
Information sources used in User Requirements report
A number of information sources were used to identify the user requirements presented in this
report. This included speaking to ONSCD staff, correspondence between users and ONSCD,
minutes of user group meetings such as the CLIP Population Sub-Group and published papers
on past consultations undertaken by ONSCD. These papers are listed below.
1. 2006-based Subnational Population Projections: Summary of part two consultation
response regarding proposals for outputs.
2. Minutes of National Population Projections Committee meeting on the National
Population Projections review, 3 June 2008.
3. Subnational Population Projections: Summary of part two consultation response regarding
projection variants, November 2008
4. Subnational Population Projections across the UK – a guidance for users, May 2010.
5. Response to the consultation on the ONS mid-2001 and mid-2002 ward population
estimates (Experimental Statistics).
6. Population bases and statistical provision: towards a more flexible future? Population
Trends 124, Summer 2006.
7. Public consultation on the reporting of migration and population statistics: Summary of
responses and future reporting.
8. 2008-based subnational population projections for England: Summary of responses to
consultation migration assumptions.
9. Summary of responses to user engagement exercise on improvements to migration and
population statistics: Summary analysis of responses and conclusions from ONS.
10. Improving Migration and Population Statistics: Analysis of responses to user engagement
exercise and conclusions from ONS.
11. UK Statistics Authority: Assessment Report 8 (Migration Statistics).
12. ONS Summary Quality Reports for:







Population estimates by marital status
Mid-year population estimates
Internal migration estimates
International migration releases
Population by country of birth and nationality
Subnational population projections
Population estimates by ethnic group
19
13. Minutes of CLIP Population Sub-Group meetings held on 30 April 2009.
14. Minutes of CLIP Population Sub-Group meeting held on 2 November 2009
15. Minutes of CLIP Population Sub-Group meeting held on 29 April 2010
20