Overview
The responsibility for running the latest censuses in the UK was split between three agencies. These were:
Office for National Statistics (ONS) for Census 2021 in England and Wales
Northern Ireland Statistics and Research Agency (NISRA) for Census 2021 in Northern Ireland
National Records of Scotland (NRS) for Census 2022 in Scotland
ONS is responsible for disseminating census statistics for the UK.
Census 2021 and 2022 UK data
Census 2021 took place in England, Wales and Northern Ireland in March 2021. Scotland's census took place in March 2022. This difference in the timing of data collection made the production of UK results more challenging than usual.
However, ONS worked with NISRA and NRS to develop a method for interpolating Scotland numbers for March 2021, allowing the creation of statistics for the UK as a whole. More details, including a range of tables produced using this method, are available at Census-based statistics, UK 2021.
Harmonisation of UK data
Harmonisation is a requirement of the Code of Practice for Statistics. This means that statistics, data and metadata should be:
consistent, for example using the same definitions and terms across different data sources and statistics
comparable, for example being aware of the differences in data or statistics
coherent, for example how well data and statistics can be combined in different ways and for different uses
Working together with other agencies
We worked closely with the Welsh Government, NISRA and NRS to ensure the censuses that took place across the UK in 2021 and 2022 were as consistent as possible. Read more about how we are worked together in:
original statement of agreement for the Conduct of the 2021 Censuses in the UK (PDF, 225KB)
Conduct of the censuses across the UK: November 2020 progress update
Conduct of the 2021 Censuses in the UK: November 2019 progress update
Conduct of the 2021 Censuses in the UK: November 2016 progress update (PDF, 321 KB)
We also organised topic-based harmonisation working groups. The aim of these meetings was to harmonise so that we could publish as much UK-wide census data as possible.
There were some differences between the censuses across the UK, such as:
- what questions were asked
- how the data were processed
- some of the methodologies used
In November 2023 we published comparability statements for variables produced by England, Wales, Northern Ireland and Scotland in our Census 2021 dictionary. Comparability statements are not available for all variables as information from Northern Ireland and Scotland was not available at the time. Find out more about variables produced for Census 2021 in Northern Ireland on the Northern Ireland Statistics and Research Agency (NISRA) website, and about those for Scotland in 2022 on Scotland's Census website.
There was also a data user working group for UK census data for 2021 and 2022. The group allowed census offices and data users to work together and give feedback. Membership included:
- the UK census offices
- academia
- research
- local authorities and county councils
- central government
- charities
- commercial organisations
Changes to UK outputs
The UK census offices committed to producing guidance on the comparability of outputs at various, to include information on:
- the level of harmonisation possible, including the time difference
- making direct comparisons for small areas across the UK
- combining data to get totals for the UK
We have published general information on data comparability in our Census 2021 dictionary. Summary aspects to consider in respect of the time difference, making small area comparisons, and the pros and cons of combining data are covered in our Census-based outputs: UK 2021, Quality and Methodology Guide.
We based mid-2021 UK population estimates on "rolled-forward" estimates from the 2021 Censuses for England, Wales, and Northern Ireland and the 2011 Census for Scotland. Rolled-forward estimates from Scotland's Census 2022 were used for Scotland from the mid-2022 population estimates onwards.
We will continue to supply UK census data to the United Nations project on the Population and Housing Census. There is no longer a requirement to submit UK census data to Eurostat.
What UK census data are used for
Information from the UK censuses helps a wide range of organisations understand the present and plan for the future. This includes public sector, private sector, third sector and academia. There is also interest from individuals.
More information
Read more about the 2011 UK Censuses, and the 2011 Census UK comparability report. You can also find 2011 Census data for the UK on the Nomis website.