Publication schedule for admin-based population and migration statistics

This article provides guidance on how we are implementing our Population and international migration statistics revisions policy to help our users understand our planned publication schedule and the availability of data in our admin-based population and migration statistical system.

Our aim is to ensure users understand and have confidence in our new approach. User feedback and local insight play an essential part in our ability to improve our population statistics. We welcome insights from users of our statistics. Please email any feedback on the publication schedule for admin-based population and migration statistics to pop.info@ons.gov.uk.

Population and migration estimates produced by the ONS

The Office for National Statistics (ONS) publishes population and migration statistics for England and Wales, and the UK. Population estimates for the UK are compiled using estimates for England and Wales produced by the ONS; estimates for Scotland are produced by National Records of Scotland (NRS); and estimates for Northern Ireland are produced by the Northern Ireland Statistics and Research Agency (NISRA). The ONS also produces, compiles and publishes international migration estimates for the UK.

Official population and migration statistics support decisions and policies across society and the economy, at national and local levels, and for different communities. Official estimates are used widely across the UK for national and local service planning. They are also used as a base for other statistics, for weighting surveys, and as a denominator for rates and ratios relating to population, health, crime and the economy.

We are working to improve our population and migration statistics by implementing new methods to make greater use of administrative data. More detail is available in our Future of population and migration: a statistical design article, published in July 2024.

Admin-based population estimates

Our admin-based population estimates (ABPEs) produced by the dynamic population model (DPM) demonstrate the potential to produce more timely and coherent estimates of the population, compared with our current mid-year estimates (MYEs).

The ABPEs are official statistics in development. We aim for the ABPEs to become our official estimates of the population in summer 2025. We will use our criteria for moving to ABPEs as official estimates of population to assess our readiness to make this move. If the criteria are met, the ABPEs will become the official population estimates for England and Wales; if they are not, the current MYEs will continue to be the official population estimates until the criteria are met.

When the ABPEs become the official population estimates, we plan to revise the population estimates data time series back to 2022 using the ABPE back series. We have selected 2022 because the ABPEs are very similar to the MYEs in 2021. This is because Census 2021 data are used to produce both estimates. This will ensure that users have a consistent time series after Census 2021.

Making ABPEs the official population estimates for England and Wales will reduce the drift in the population estimates that can result from accumulating uncertainty between censuses, as demonstrated in Section 3 of our Transforming population statistics, comparing 2021 population estimates in England and Wales article. In the future, the DPM will provide population estimates each year, as well as the components of change between that year and the previous. We are exploring options to ensure that when ABPEs become the official population estimates, the associated components of change for the year to mid-2022 are consistent with estimates for mid-2021.

Long-term international migration

Our UK long-term international migration (LTIM) estimates have been primarily admin-based migration estimates since 2021. They are currently official statistics in development, which reflects the continuing development of our approach to estimating long-term international migration. More information is available in our Developing our international migration estimates blog.

We are working towards coherence in the admin-based population and migration system for England and Wales. We are exploring the potential for international migration estimates to be produced via the DPM for England and Wales to ensure consistency with the admin-based population estimates. As the DPM produces estimates for England and Wales only, we will also explore methods to continue producing coherent LTIM estimates for the whole of the UK.

Revisions are necessary when timely estimates are produced. We recognise the wide-ranging use of these statistics, so are setting out how we balance accuracy, timeliness and the pragmatic need for stable estimates.

In statistical outputs, we refer to the planned updates resulting from improvements to data or methods as scheduled revisions. We recognise the potential need for revisions to our estimates, as reflected in the Population and international migration statistics revisions policy and the Code of Practice for Statistics. In this article we are clarifying our revisions approach for the population and migration statistics system.

Scheduled revisions have two strands:

• regular revisions, where we replace provisional estimates with improved updated estimates using additional data that have become available

• methods and data source improvements: where we update the published back series using improved methods or new data sources

Unscheduled corrections are not covered in this article. We will publish updates at the earliest opportunity following the principles outlined in the Population and international migration statistics revisions policy.

Long-term international migration (LTIM) refers to people entering or leaving the UK for a period of at least 12 months, which is consistent with the UN definition for long-term migrant.

To produce timely estimates, we produce an estimate of migration around five months after the reference period. This means that, when we publish the provisional LTIM estimates, we do not have all the travel information available and make assumptions about how long new arrivals are likely to stay in the UK. Over time we can see whether a migrant has interacted with admin data sources, which then enables us to update our estimates based on actual behaviours for the latest time periods.

International migration contributes to change in the population estimates under both the traditional cohort component method and the dynamic population model (DPM). Any revisions to the international migration estimates will result in population estimates revisions for both methods.

We publish provisional estimates of international migration around five months after the reference period, which are updated with additional data around 11 months after the reference period. International migration data mature around 17 months after the reference period, when assumptions and data adjustments are replaced with actual data reflecting observed behaviour.

To improve coherence between the admin-based population estimates (ABPEs) and LTIM, ABPEs will be updated, two years after the reference period. This is outlined in Section 4: Publication and revisions schedule. Following this, they will not be updated again unless there is a revision to the published back series to incorporate improved methods or new data sources, or a correction. We are considering the content and timing of the provisional ABPEs and will provide an update on plans when we publish the mid-2024 ABPEs.

This section describes the currently planned publication and revisions schedule for population and international migration estimates over the next two years. It includes both regular revisions and revisions resulting from improved methods and new data sources. This schedule may change over time as we make improvements to our admin-based statistics and consider the content and timing of the provisional admin-based population estimates.

From 2026, when we aim for the methods for the dynamic population model (DPM) and international migration estimates to be largely stabilised, we plan to implement revisions to the published back series in the periods specified in Section 6: Methods and data source improvements.

In this section "LTIM" refers to long-term international migration and "ABPE" refers to admin-based population estimates. Figure 1 provides a visualisation of the currently planned publication and revisions schedule.

Provisional LTIM estimates for the UK for year ending December 2024

• Date of publication: May 2025.

• New data: provisional estimates for year ending (YE) September 2024 and YE December 2024.

• Period being revised: first-updated estimate for YE March 2024 and YE June 2024, and second-updated estimate for YE September 2023 and YE December 2023.

• Revisions to published back series: none.

ABPEs for England and Wales for mid-2024

• Date of publication: summer 2025.

• New data: first published estimates for mid-2024 should be considered equivalent to first-updated ABPEs; we did not produce provisional ABPEs for mid-2024.

• Period being revised: second-updated estimate for mid-2023.

• Revisions to published back series: from mid-2022.

• Reasons for revisions: method changes included in November 2024 LTIM and possible DPM method changes.

Provisional LTIM estimates for the UK for YE June 2025

• Date of publication: November 2025.

• New data: provisional estimates for YE March 2025 and YE June 2025.

• Period being revised: first-updated estimate for YE September 2024 and YE December 2024, and second-updated estimate for YE March 2024 and YE June 2024.

• Revisions to published back series: likely from YE June 2021.

• Reasons for revisions: improvements to methods.

Provisional ABPEs for England and Wales for mid-2025 (subject to change)

• Date of publication: late 2025 or early 2026.

• New data: provisional estimate for mid-2025.

• Period being revised: no revisions.

• Revisions to published back series: none.

Provisional LTIM estimates for the UK for YE December 2025

• Date of publication: May 2026.

• New data: provisional estimates for YE September 2025 and YE December 2025.

• Period being revised: first-updated estimate for YE March 2025 and YE June 2025, and second-updated estimate for YE September 2024 and YE December 2024.

• Revisions to published back series: none currently planned.

Updated ABPEs for England and Wales for mid-2025

• Date of publication: summer 2026.

• New data: none.

• Period being revised: mid-2025 and mid-2024, to provide first- and second-updated estimates, respectively.

• Revisions to published back series: possible.

• Reasons for revisions: LTIM revisions included within the YE June 2025 release or DPM method improvements.

Provisional LTIM estimates for the UK for YE June 2026

• Date of publication: November 2026.

• New data: provisional estimates for YE March 2026 and YE June 2026.

• Period being revised: first-updated estimate for YE September 2025 and YE December 2025, and second-updated estimate for YE March 2025 and YE June 2025.

• Revisions to published back series: none currently planned.

Provisional ABPEs for England and Wales for mid-2026 (subject to change)

• Date of publication: late 2026 or early 2027.

• New data: provisional estimate for mid-2026.

• Period being revised: no revisions.

• Revisions to published back series: none.

Figure 1: Planned publication and revisions schedule for admin-based population and migration statistics

Notes:

1. This schedule may change over time as we make improvements to our admin-based statistics and consider the content and timing of the provisional admin-based population estimates.

Download this image Figure 1: Planned publication and revisions schedule for admin-based population and migration statistics

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Provisional estimates provide an early indication of the estimate because they include assumptions and adjustments to the data. They are likely to be revised, and therefore caution is advised when using these estimates for policy and funding decisions.

First-updated estimates include additional data alongside refined assumptions and adjustments. These will have a lower level of uncertainty than the provisional estimates.

Second-updated estimates are updated for the second time around 17 months after the reference period for migration and in the summer two years after the reference period for population. These estimates provide our most accurate estimate, where all adjustments and assumptions are replaced with data. These will have a lower level of uncertainty than the first-updated estimates and should be used for any work that requires more stability.

Revisions to population and international migration statistics have wide-reaching implications and the need for them must be carefully assessed. There are implications for direct users of population and international migration statistics and for the producers of other statistical series or outputs. For this reason, we must balance the need for the most accurate and timely estimates with the need for stability. We will manage the frequency of revisions to the published back series to provide this balance.

It is our intention that from autumn 2026, the published back series will only be open for revisions at fixed intervals that are communicated to users. This will be every three years while our methods are still in development, and every five years, once they have matured.

We will not revise the published back series in these intervals if the changes are going to be small. A set of criteria will be developed to decide when the published back series should be revised. For example, if the current methods cannot continue or if improved methods or new data sources lead to estimates which lie outside the uncertainty measures for the existing estimates.

If the criteria are not met, we will not revise and will reassess when we reach the next review point. In exceptional circumstances, we may need to make changes outside of the three- or five-year fixed intervals, if substantial improvements to the estimates are identified based on our criteria.

From 2026, it is currently planned that changes to methods and data sources will only be implemented when provisional estimates are produced in autumn for international migration and winter for population estimates. We will publish methods articles outlining the impact of these changes to population and migration estimates and warn users of expected revisions to the published population back series the following summer.

As population and migration statistics evolve, our revisions schedule may need to be amended. Our Dynamic Population Model is flexible with the ability to incorporate new data sources and adapt to quality issues so we can continually improve our statistics to better meet user needs.

Under our current mid-year estimates (MYE) system, there are planned revisions in the 10-year period leading up to the next census. Following a census, the MYEs are rebased, after which they are normally closed to further revisions.

After we have stabilised our methods for the admin-based population estimates (ABPEs) and long-term international migration (LTIM) estimates, we intend to move towards a 10-year cycle of closing the back series to further revisions.

We are planning to follow the MYE approach and only revise back series for one decade at a time, with the first decade starting in 2021 and closing in 2031. The estimates in each decade can be revised in the three- or five-year review intervals outlined in Section 6: Methods and data source improvements. 

A final decision on how frequently we close the back series for further revisions will depend on our approach to coverage adjustment and any other developments in the future migration and population statistics system. We will keep users updated on our plans.

The differences between the provisional, first-updated and second-updated admin-based population estimates (ABPEs) for England and Wales have been small, even though there have been both data and methods changes. For example:

• the first-updated ABPE for England and Wales for mid-2023 was 0.1% lower than the provisional ABPE

• the second-updated ABPE for mid-2022 was relatively unchanged from the provisional ABPE

• the second-updated ABPE for mid-2022 was 0.2% lower than the first-updated ABPE

• the first-updated ABPE for mid-2022 for England and Wales was 0.2% higher than the provisional ABPE

There is more variation in the size of the revisions at the total local authority level, as shown in Figure 2.

Figure 2: The differences between provisional, first-updated and second-updated ABPEs vary by local authority, with the largest differences generally found in cities and London boroughs

Percentage difference between provisional, first-updated and second-updated admin-based population estimates (ABPEs) for mid-2022 and mid-2023, local authorities in England and Wales

Notes

1. Estimates for local authorities with small populations may be less robust than larger local authorities. 

2. The Isles of Scilly and City of London have very small populations, which can often lead to outlying results. For this reason, they are not included in this chart but are included in the dataset download.

In October 2024, we published our Admin-based population estimates; England and Wales engagement plan 2024 to 2025. It is important to us that we understand and consider the views of those who use our statistics before decisions are finalised. This includes our future approach to revisions.

To inform our approach, we shared early proposals and refined them based on feedback. This included engagement with colleagues at the Office for National Statistics (ONS), devolved governments, the UK Population Theme Advisory Board (UKPTAB), central government departments, local authorities and the Migration Statistics Expert Group.

We will continue to keep users of our statistics informed and welcome feedback on our proposed approach. You can receive updates via our monthly newsletter and our series of upcoming webinars. Please email any questions or feedback to pop.info@ons.gov.uk

Administrative data

Collections of data maintained for administrative reasons, for example, registrations, transactions or record-keeping. They are used for operational purposes and their statistical use is secondary. These sources are typically managed by other government bodies.

Dynamic population model

The Dynamic Population Model (DPM) is a statistical modelling approach that uses a range of data to measure the population and population changes in a fully coherent way.