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Office for National Statistics are investigating alternative methods for producing population estimates by ethnic group.

New approaches for producing population estimates by ethnic group report

Introduction

Office for National Statistics (ONS) publishes detailed population estimates by ethnic group for areas in England and Wales following each census. However, there are currently no reliable population estimates by ethnic group available at the local authority level for the years between censuses. Given the user interest in regular, local authority ethnicity data, ONS has been investigating alternative methods to meet this need.

Today (25 August 2017) we have published:

  • a research note, accompanied by illustrative estimates for 2016, on a method of combining data from the Census and the Annual Population Survey (APS) to produce population estimates by ethnic groups for UK countries and local authorities and higher levels in England and Wales – which begins to address user interest for more current information on ethnicity
  • an approach for estimating ethnicity from survey and administrative data at the local authority level – which is an investigation into the longer-term potential of using administrative data as well as surveys

These research articles respond to a user need for more regular and robust estimates of ethnicity. In particular we’re investigating a strategic approach, using combinations of the data we currently have available and methods that can be developed and refined over time. These publications take on recommendations from users to investigate a wider range of data sources, the use of social survey sources and small area estimation techniques. Today’s publications make progress in these areas.

Background

Formal annual estimates of the population by ethnic group were first published (for LAs in England only) by ONS in 2006. These Population Estimates by Ethnic Group (PEEGs) continued to be published as experimental statistics until 2011.

These estimates were produced using the standard cohort-component method used for the official mid-year population estimates. The cohort-component method ages forward the census population one year, then accounts for births, deaths, international migration and special populations such as the armed forces. The PEEGs extended the mid-year population estimates by using other data-sources (most notably the 2001 Census) to estimate the ethnic composition of each component of population change - births, deaths, and migration.

While the PEEGs approach had several advantages, comparison with other data sources suggested that the estimates may have drifted from the true values for some sub-national areas. For example, the 2009 PEEGs estimated that the White British group made up 60% of the population of London while the Annual Population Survey (APS) estimated the proportion as 51%. One possible cause for this difference was the lack of a reliable method for estimating the ethnic composition of internal migration (the largest component of population change for local authorities).

Since 2012, users have relied on the results of the 2011 Census as providing the best picture of the ethnic composition of the population. However, we have identified increasing user interest in updated estimates as the 2011 Census results become less current. The research articles described below reflect our progress towards producing outputs that meet this user need.

APS-based population estimates by ethnic group

We already publish estimates of the population by country of birth and nationality at local authority level. These estimates are derived directly from the Annual Population Survey (APS) and are not aligned with the mid-year population estimates. Today we have published a Population Estimates by Characteristics research paper describing a simple method of adjusting the APS results so that estimates consistent with the mid-year estimates can be produced. We also describe the use of this method to derive population estimates by ethnic group and publish a set of tables containing illustrative estimates for 2016. This method provides a quick and easy way of estimating the population by ethnic group in the decade following the 2011 Census.

An approach for estimating ethnicity from survey and administrative data

The Research outputs: An approach for estimating ethnicity from survey and administrative data research paper describes early research investigating the ability to produce estimates of ethnicity in an Administrative Data Census context. Ethnicity data is important to users, however our initial research finds that ethnicity information is not widely collected on administrative sources and the statistical quality, for the purpose of producing estimates, varies. The approach uses the Generalised Structure Preserving Estimator (GSPREE) approach to make the best use of available data, combining survey and administrative data sources to produce population estimates by ethnic group. This approach offers flexibility in terms of being able to incorporate new data sources as they become available.

As this represents an early investigation into the approach, this report focuses on the methods used and an analysis of how well they perform. Estimates are not published alongside the report at this stage.

However later in 2017, a follow-up report will use this method to produce mid-decade estimates for 2015 using an administrative data population base. This will enable further comparisons to be made between the two methods described in today’s releases.

Main differences between the approaches

The individual reports provide further details on methodological approaches, the key differences are summarised below:

Feedback and next steps

We are keen to get feedback on these approaches including how they might be improved and potential uses of the data. Please email your feedback to pop.info@ons.gov.uk. Don't forget to include the title of the report in your response.

We plan to publish further analysis on the differences between the approaches later in 2017.