Population estimates by output areas, electoral, health and other geographies, England and Wales: rebased mid-2012 to mid-2020

• Population estimates for lower and middle layer Super Output Areas (LSOA and MSOA, respectively) for mid-2012 to mid-2020 have been rebased to align with Census 2021 results.
• Population estimates for mid-2011 to mid-2022 are now available on the statistical geographies used for Census 2021.
• Population estimates below local authority level for mid-2022 have been revised in line with changes to our mid-2022 local authority level estimates published in July 2024.
• Population estimates for wards, Parliamentary constituencies, integrated care boards, and National Parks for mid-2012 to mid-2020 and mid-2022 have also been revised.

The data published in this release provide population estimates on Census 2021 lower layer Super Output Areas (LSOAs) and middle layer Super Output Areas (MSOAs) between mid-2012 and mid-2020. They are consistent with our rebased local authority estimates published in November 2023. In addition, estimates for mid-2022 have been revised to be consistent with our local authority level estimates published in July 2024.

Estimates for LSOAs by broad ages and MSOAs by five-year age groups are accredited official statistics. Estimates at greater levels of disaggregation, for example by single year of age and for output areas, are provided as supporting information. This enables aggregation to meet individual user requirements. Estimates for output areas are only available from NOMIS.

This release includes estimates for Parliamentary constituencies, electoral wards, integrated care boards, and National Parks, alongside population estimates for statistical geographies. Estimates by Parliamentary constituencies and electoral wards are published exclusively on NOMIS.

Estimates for electoral wards, Parliamentary constituencies, and National Parks are official statistics in development. Estimates for integrated care boards are aggregated directly from lower layer Super Output Areas (LSOAs) and are accredited official statistics.

Population estimates by output areas, electoral, health and other geographies for England and Wales for mid-2023 and beyond

We will publish estimates for mid-2023 for England and Wales after revisions are made to mid-2023 local authority estimates in summer 2025. This will be alongside a first release of mid-2024 local authority estimates.

We are exploring possible approaches for producing admin-based population estimates (ABPEs) for geographical breakdowns below local authority level for England and Wales. We explore possible approaches in our Geospatial methods for Small Area Population Estimates: proof of concept article.

Admin-based population estimates for England and Wales

We are aiming to make our admin-based population estimates (ABPEs) the official mid-year population estimates for England and Wales in 2025 at local authority level and above. We will continue our programme of engagement with users of population statistics to understand the effect these changes will have before decisions are made. This includes setting criteria for moving to ABPEs as the official estimates for England and Wales, which we plan to share in January 2025. This will be based on conversations with our partners, including devolved governments and central government departments.

We are undertaking engagement through autumn 2024 to gather feedback on the new approach, including with local authorities. This is so we can draw on local insight as we improve our estimates. We requested an assessment of our admin-based population estimates. We are working to address the points in the assessment to meet the standards expected of accredited official statistics in 2025.

Feedback from anyone who uses these statistics is welcomed at any time. You can email us about the approach we are taking at pop.info@ons.gov.uk.

Population estimates

Population estimates provide statistics on the size and age structure of the population. They are the official source of estimated population size in between censuses and inform a wide range of official statistics.

Mid-year

Mid-year refers to 30 June of any given year.

Usually resident population

These data estimate the “usually resident population”. This is the standard United Nations (UN) definition and includes only people who reside in a country for 12 months or more, making them usually resident in that country. As such, visitors and short-term migrants are excluded.

Super output areas

Super Output Areas (SOAs) are statistical geographies designed to improve the reporting of small area statistics. They are built from groups of census Output Areas, are of a consistent population size, and are not subject to boundary changes between censuses. A simple guide to the UK geographical areas frequently used for the publication of official statistics can be found in our A beginner’s guide to the UK geography.

There are two broad types of small area population estimates, both of which are included in this release.

The main products are the estimates for Super Output Areas (SOAs), which are based on Census 2021 and rolled forward annually using a ratio change methodology. This approach uses the change in the population recorded in the Personal Demographics Service (based on GP registrations) as an indicator of the change in the true population.

Estimates for lower layer SOAs (LSOAs) by broad ages and middle layer SOAs (MSOAs) by five-year age groups are accredited official statistics. Estimates at greater levels of disaggregation, for example by single year of age, are provided as supporting information only. More information can be found in our Small Area Population Estimates: Summary of methodology review and research update.

The remainder of our small area population estimates products relate to a range of different geographic areas and are derived directly from the SOA figures. First, estimates for LSOAs are broken down to Output Area (OA) level using an apportionment approach. These OA estimates are then aggregated to produce estimates for electoral wards and Westminster Parliamentary constituencies on a best-fit basis. Estimates for National Parks are also calculated from the OA-level data.

Electoral wards, Westminster Parliamentary constituencies, and National Parks are official statistics in development. Estimates for health geographies are aggregated directly from LSOAs and are accredited official statistics.

The estimates for output areas, along with geography lookups from the Office for National Statistics (ONS) Open Geography Portal, enable additional geographic breakdowns to be produced.

Small area population estimates are used by both central government departments and local authorities for a range of purposes. These include planning and monitoring of services and as denominators for the calculation of various rates and indicators.

The mid-2011 to mid-2022 small area population estimates covered by this release are fully consistent with our mid-year population estimates, including local authorities, regions, and the national total for England and Wales. A full description of the methods used to calculate all small area population estimates is available in our methodology note.

In some local authorities, the number of people included on the Personal Demographics Service in any current year may have increased or decreased in many LSOAs and MSOAs, compared with the previous year. This may be because of changes in administrative practices or may reflect genuine population change. The process of constraining LSOA and MSOA estimates to previously published local authority population estimates means that this pattern is not automatically reflected in the mid-year estimates.

All population estimates are subject to statistical uncertainty, and this is generally highest for estimates of small areas, areas with high levels of population churn, and at the end of the inter-census period.

More quality and methodology information

More quality and methodology information (QMI) on strengths, limitations, appropriate uses, and how the data were created is available in our Population estimates by output areas, electoral, health and other geographies QMI.