Combining and comparing census figures across the UK

10 Apr 2025 12:15 PM

Population censuses offer the most comprehensive and detailed data available on a wide range of characteristics of the UK population. Traditionally, they have been carried out at the same time in all four countries of the UK and the results have been brought together to produce overall UK statistics.

A single UK census date was also the intention for 2021, but the circumstances of the coronavirus (COVID-19) pandemic led to Scotland’s census being delayed by a year. This means that Census Day was 21 March 2021 in England, Wales and Northern Ireland, but 20 March 2022 in Scotland. This difference in the timing of data collection makes the production of UK results more challenging than usual.

The three agencies that run the censuses – the Office for National Statistics (ONS, covering England and Wales), National Records of Scotland (NRS) and the Northern Ireland Statistics and Research Agency (NISRA) – have been working together to develop a solution. In doing so, we have sought to balance simplicity and viability against the wish to create UK numbers for a consistent time point.

The method we have developed is to create statistics for Scotland for March 2021 and add them to the equivalent census totals from the rest of the UK. Our approach for Scotland is based on interpolation between their 2011 and 2022 censuses, also constraining the results to ensure consistency with their official population and household estimates from 2020 and 2021.

We will use this method to create a set of tables at UK and country level, offering insight into how a range of UK statistics may have looked if the censuses had all been in March 2021. The Scotland values will not, however, replace NRS’s Census 2022 results as the definitive census statistics for Scotland.

We will not be producing statistics below country level because the use of interpolation for smaller areas is additionally challenging, with the quality of the resulting values liable to be lower. We therefore recommend that comparisons between local areas in different parts of the UK should be based on the respective 2021 and 2022 census data. Users should, however, be aware of any factors that may complicate direct comparability between those dates.

We will publish the tables in the coming months, together with more detailed guidance on approaches to creating and comparing data across the UK.

If you have any feedback on this note, please contact pop.info@ons.gov.uk.