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

• The UK population at mid-year 2021 was estimated to be 67.0 million, an increase of 3.7 million (5.9%) on the population in mid-2011.

• Over the 10 years between 2011 and 2021, the population of England increased by 6.5% to an estimated 56,536,000, the highest rate of the four countries of the UK; the estimated population of Northern Ireland increased by 5.0% to 1,905,000, Scotland by 3.4% to 5,480,000, and Wales by 1.4% to an estimated 3,105,000.

• The mid-2021 population estimates for England, Wales and Northern Ireland are based on the 2021 censuses for England, Wales, and Northern Ireland.

• For Scotland, the mid-2021 population estimates are rolled forward from mid-2020, as Scotland's census was moved to 2022 because of the impact of the coronavirus (COVID-19) pandemic; this means that population estimates based on Scotland's Census 2022 are not yet available.

We estimate the UK population in mid-2021 to be 67.0 million (67,026,292). This is an aggregate of the estimates for the four constituent countries. For England, Wales, and Northern Ireland these are the first mid-year population estimates based on the 2021 censuses for these countries. For Scotland the mid-2021 population estimates were rolled forward from mid-2020 as the census in Scotland took place in March 2022, a year later than the rest of the UK, because of the impact of the coronavirus (COVID-19) pandemic.

The mid-2021 population estimates are primarily based on the 2021 censuses (for England and Wales, and Northern Ireland). The usual resident population as at Census day (21 March 2021), by single year of age, is aged on to 30 June 2021 and then births, deaths and migration are accounted for.

Censuses provide the most accurate estimate of the population and therefore the reliability of mid-year estimates is very high immediately following a census. The figures will be revised in the next two years to include updated estimates for Scotland, incorporating the 2022 Census for Scotland. We will also incorporate revisions to international migration data as we continue our transformation of population and migration statistics.

All four countries of the UK saw population increases in the decade between mid-2011 and mid-2021. Table 1 shows the populations and summary statistics for each country of the UK. The highest percentage increase was in England where the population increased by 3.4 million, a rise of 6.5% between 2011 and 2021. Northern Ireland saw the next highest percentage increase of 5.0%, followed by Scotland at 3.4% and Wales at 1.4%.

Overall, England had the highest population density of the four countries of the UK at mid-2021. However, this includes a wide variation within England, where the population density in London was 5,596 people per square kilometre (km) and the South West was 240 people per square km.

The median age of the population in the UK was 40.7 years in mid-2021, a year higher than in mid-2011. The increase in median age over the decade was highest in Northern Ireland, though at 39.8 years, this was still the lowest of the countries in the UK. Wales had the highest median age at 43.1 years.

Figure 1 shows the percentage change in population of the UK during the fifty-year period from mid-1971 to mid-2021. The population of the UK increased by approximately 11.1 million (19.8%) during the last fifty years and by approximately 3.7 million (5.9%) during the last decade. Population growth in the latest decade was lower than the previous decade in all four UK countries.

The mid-2021 population estimate for England and Wales was 59,642,000, with the population for England at 56,536,000 and Wales at 3,105,000. Census 2021 for England and Wales took place on 21 March 2021 and the mid-year population estimates for England and Wales are based on these with adjustments made for ageing, births, deaths and migration in the 101 days until 30 June 2021.

During the period between census day and mid-year 2021, most restrictions related to the coronavirus (COVID-19) pandemic were lifted. However, restrictions were lifted on different dates in England and Wales. Alongside the lifting of restrictions, COVID-19 vaccinations were made available to all adults. The rollout of vaccinations resulted in greater interaction between individuals and the administrative data that we use to measure internal migration (movement between one part of the UK and another). We have adjusted our methods to account for this by using Census 2021 data. Full details on this can be found in our Population estimates for the UK, mid-2021 methodology guide.

Components of change between census day and mid-year 2021 in England and Wales

The mid-2021 estimates are based on Census 2021 and produced using the following method:

• ageing on the estimates from Census 2021 for England and Wales, by single year of age and local authority

• adding the births in England and Wales for the period between Census 2021 and mid-year 2021 (171,000) and subtracting deaths (132,000)

• accounting for net international migration (1,000) and internal migration (5,000)

• no adjustments for either prisoners or home or foreign armed forces personnel have been made

For the UK as a whole, net international migration for the year to mid-2021 was an estimated 173,000 and for England and Wales it was an estimated 156,000. However, net international migration for the quarter of the year between April and June 2021, for England and Wales, was close to zero (an estimate of around 1,000). This reflects seasonal patterns in migration and covers the period where international travel was restricted following the coronavirus pandemic. Home Office statistics on passenger arrivals into the UK show that air travel began to recover from July 2021.

Internal migration for England and Wales

In the period between Census day and mid-year 2021 we estimate that around 5,000 more people moved to England and Wales from the rest of the UK than left. This contrasts with most periods where a higher number of people move from England and Wales to other parts of the UK.

Rebasing and reconciliation

The Office for National Statistics (ONS) will conduct reconciliation work for mid-year population estimates to understand how and why the estimates based on Census 2021 for England and Wales differ from those based on the mid-year estimates rolled forward from the 2011 Census. The insights gained will be used to improve the production of future population estimates and will result in a revised back series of population estimates for the period 2012 to 2020. This back series will increase the coherence between the census and mid-year estimates. The provisional publication date is early 2023 for reconciliation and spring 2023 for rebasing.

The Northern Ireland Statistics and Research Agency (NISRA) will conduct reconciliation and rebasing work to understand how and why the estimates based on Census 2021 for Northern Ireland differ from those based on the mid-year estimates rolled forward from the 2011 census. Further information can be found in Mid-year population estimates for Northern Ireland: 2021.

Mid-2022 population estimates

We plan to publish population estimates for England and Wales in Summer 2023. The Northern Ireland Statistics and Research Agency (NISRA) also plan to release mid-2022 population estimates in Summer 2023. Details of its release plans can be found in its Population Statistics Work Plan.

Mid-2022 population estimates for Scotland will be based primarily on the results of the 2022 Census adjusted for births, deaths and migration in the period between census day and mid-year and are currently scheduled to be published in winter 2023 to 2024.

Population and migration statistics transformation

The census has evolved throughout the decades, providing an insight every 10 years into who we are and how we live. While the census and mid-year population estimates based on the census provide the best picture of society at a moment in time, how the ONS produce population and social statistics is changing.

We are using a variety of data sources to provide more frequent, relevant, and timely statistics. This will allow us to understand population change in local areas this year and beyond.

Our Dynamic population model for England and Wales: November 2022 article was the second in a series of publications that outlined our plans to transform population and migration statistics. It described our initial research into a dynamic population model (DPM).

In early 2023, we will publish our research on provisional June 2022 population estimates for all local authorities.

For more information, see How we are improving population and migration statistics.

Components of change

Components of change are the factors that contribute to population change. This includes births and deaths (referred to as natural change) and net migration. Migration includes movements of people between the UK and the various countries of the world (international migration) and between local authority areas within the UK (internal migration).

Usually resident population

These data estimate the usually resident population. The standard United Nations definition is used, including 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.

Rolled forward

Rolling forward refers to the practice of using the population estimate from the previous reference date as the starting point for estimating the population at the current reference date. The previous population estimate is aged on and data on births, deaths and migration are used to reflect population change during the reference period.

Ageing on

The process of adjusting the age of the base population to the reference period. For the mid-2021 estimates, the base population is aged on by the period of time between the census and 30 June (101 days).

Internal migration

Internal migration describes moves made between local authorities, regions or countries within the UK. Unlike international migration, there is no internationally agreed definition.

Median age

Median age is the age that divides a population into two numerically equal groups (that is, half the people are younger than this age and half are older).

Net flow

The net flow is the inflow minus the outflow. Positive net flows (greater than zero) indicate the inflow is larger than the outflow, that is, a net inflow. Negative net flows (less than zero) indicate the outflow is bigger than the inflow, that is, a net outflow.

Quality

The mid-year estimates for England and Wales are produced by the Office for National Statistics (ONS). The mid-year estimates for Scotland are produced by National Records Scotland (NRS) and the mid-year estimates for Northern Ireland by the Northern Ireland Statistics and Research Agency (NISRA).

Estimates are produced by updating a census base using a standard demographic method, the cohort component method, and cover the usually resident population. The mid-2021 population estimates are primarily based on the 2021 censuses (for England and Wales and for Northern Ireland). The resident population as at Census day (21 March 2021), by single year of age, is aged on to 30 June and then flows are applied to cover births, deaths and net migration. Censuses provide the most accurate estimate of the population and therefore the reliability of these mid-year estimates is very high immediately following a census.

For Scotland, the mid-2021 population estimates are rolled forward from mid-2020, as Scotland's census was moved to 2022 because of the impact of the coronavirus (COVID-19) pandemic.

Detailed information on the methods and data sources used can be found in the following methodology guides:

• Population estimates for the UK, mid-2021: methods guide
• Methodology paper - Mid-year population estimates for Northern Ireland (PDF, 257KB)
• Mid-year population estimates Scotland: Methodology guide (PDF, 284KB)
• Consistency of methods used for population statistics across UK countries

More quality and methodology information on strengths, limitations, appropriate uses, and how the data were created is available in our Mid-year population estimates Quality and Methodology Information (QMI) report.

The following quality information is also available.

• Quality Indicators indicate the percentage of a local authority population that consists of difficult to estimate population groups.

• For local authority population estimates in England and Wales, confidence intervals from Census 2021 are available in the tool to compare age-sex estimates in Census 2021 (XLS, 2.39MB); these confidence intervals reflect most of the uncertainty in the 2021 mid-year estimates, in 2023, we will publish measures of uncertainty for the mid-2021 population estimates, reflecting change between census day and mid-year.

If you would like to provide feedback on local level population estimates, with the aim of adding commentary to such statistics and informing future research, use the Population estimates: contextual information feedback form.

Strengths

• These are the official population estimates of the UK, and are primarily based on the 2021 censuses (for England and Wales, and Northern Ireland).
• Mid-year population estimates for reference periods immediately following a census are considered to be highly reliable.
• Information from administrative registers, such as the numbers of births and deaths, is considered to be very reliable.
• Estimates include data on moves between local authorities and between countries of the UK (internal migration).

Limitations

• The data are not counts, rather they are estimates created by combining many different data sources.
• The data sources used are the best available on a nationally consistent basis down to local authority level, but the estimates are subject to the coverage and error associated with these sources.
• Data for Scotland are based on the 2011 Census and rolled-forward from mid-2020. This is a different census base to the other UK countries.
• International migration is estimated using multiple data sources and is subject to particularly high uncertainty; we expect revisions to international migration to be made in the next year.