Skip to main content

Population estimates for Wales, the UK, England, Scotland, and Northern Ireland: Mid-2021

The 2021 mid-year estimates of the population for Wales and UK countries were published on 21 December 2022 by the Office for National Statistics (ONS). For Wales, England, and Northern Ireland, these are the first population estimates to be based on the 2021 censuses for these countries. For Scotland, the census was moved to 2022 (due to the impact of the COVID-19 pandemic) with the mid-2021 population estimates being rolled forward from mid-2020 using the standard method.

  • The 2021 mid-year estimate of the population of Wales was 3,105,000, an increase of 1.4% (42,000) on the mid-2011 estimate.
  • People aged 65 years or older were estimated to account for just over a fifth of the total population in Wales in mid-2021, the highest proportion of all UK countries (21.4% in Wales, or 666,000 people).
  • 60.9% of the population were aged 16 to 64 years in mid-2021 (around 1,893,000 people).
  • Children and young people aged 0 to 15 years old accounted for the remaining 17.6% of the population in mid-2021 (547,000 children and young people).
  • The 2021 mid-year estimate of the UK population (ONS) was 67,026,000, an increase of 3.7 million (5.9%) on the population in mid-2011.

Census 2021 estimated that the population of Wales was around 3,107,500 on Census Day, 21 March 2021. The population of Wales is estimated to have decreased slightly in the period between Census Day (21 March) and 30 June 2021, by around 2,000 people. This is due to negative natural change (fewer births than deaths), and negative net migration (more people moving out of Wales than moving into Wales) during this period. Negative net internal migration (more people moving out of Wales to other parts of the UK than moving in) between Census Day and 30 June 2021 is partly due to students and graduates moving from term-time addresses to non-term time addresses during this period. However, patterns of population change in this period may also reflect some impacts related to the pandemic, as many of the restrictions in place at Census Day had been lifted by 30 June 2021.

The ONS has stated that the mid-year estimates for the UK will be revised in the next two years to include updated population estimates for Scotland, incorporating the 2022 census for Scotland, as well as revisions to international migration data as part of their transformation of population and migration statistics. Data is available on StatsWales.

Reconciliation of mid-year population estimates with Census 2021, Wales and England

On 28 February, the ONS published the Reconciliation of mid-year population estimates with Census 2021, England and Wales.

This was followed by the publication of Reconciliation of mid-year population estimates with Census 2021 at local authority level (ONS) on 2 March.

Reconciliation is the process of comparing the new official mid-year population estimates for mid-2021 (derived from using Census 2021 data), with the mid-year population estimates for mid-2021 rolled forward from 2020. The rolled forward estimates indicate what the ONS would have estimated the population to be in the absence of Census 2021.

  • The official mid-2021 population estimate for Wales, based on Census 2021 data, is 66,800 (2.11%) lower than the estimate rolled forward since Census 2011.
  • For Wales, the difference is made up of 22,500 more females and 44,300 more males in the 2021 rolled-forward estimate.

The articles include information on the possible causes of the differences and examines the impacts of the differences on the age and sex makeup of the population, and at the country and regional levels.

2020-based interim national population projections: year ending June 2022 estimated international migration variant

On 27 January, the ONS published the 2020-based interim national population projections: estimated international migration variant. This data-only release provides new international migration assumptions that have been developed following the latest expert advice and latest provisional estimates of international migration. These projections are a variant of the previously published 2020-based interim national population projections.

Census 2021

Create a custom dataset

On 28 March, the ONS published a flexible table builder for Census 2021 data, also known as the Create a custom dataset tool (ONS).

For the first time, this allows users to look for interactions between topics which are important to them and build their own datasets. The ONS has published a blog to accompany this tool, which includes a short video explaining how to create your own custom datasets.

Electoral roll

The Electoral roll 2022 statistics for Wales are due to be published on 20 April.

Welsh language statistics

For information on Welsh language statistics, please see the Statistics Wales quarterly update.

Contact details

Martin Parry

Telephone: 0300 025 0373



Telephone: 0300 025 8099