National population projections, migration assumptions: 2024-based

This methodology article provides supporting methodology information for the migration assumptions used in the 2024-based national population projections (NPPs), including the principal and variant assumptions.

Demographic behaviour, and migration in particular, are inherently uncertain and complex. The international migration assumptions are not intended to forecast or predict future migration levels. Long-term assumptions should be interpreted as a potential scenario in which future net international migration averages at a certain level. As these patterns in international migration change, we will adjust assumptions in future projections releases accordingly.

The principal international migration assumption used in the 2024-based NPPs assumes that net international migration to the UK remains constant at 230,000 per year from mid-2027 onwards. This is referred to as the "long-term assumption" and it is informed by a 10-year average of international migration data (for the 10 years ending mid-2013 to mid-2021 and mid-2025). We have reduced our assumption for net international migration from 340,000 in our 2022-based NPPs, following engagement with our Migration Expert Advisory Panel and review of the latest data, which showed a steep decrease in levels of net migration.

For mid-2025, the latest provisional estimate of international migration has been used where available for England, Scotland, and Wales, after which short-term assumptions are effective for mid-2026.

In addition to the principal projection, three variant projections have been produced to show how the UK population might change under alternative migration scenarios. These variant projections include higher and lower levels of international migration than that assumed in the principal projection, and a scenario with no international or cross-border migration from the base year.

International migration numbers for the UK differ to those in the UK estimates of long-term international migration for some years. This is because the estimates for Northern Ireland used in the NPPs include international migration estimates published by Northern Ireland Statistics and Research Agency (NISRA), which differ from Office for National Statistics (ONS) estimates.

Migration assumptions in national population projections (NPPs) are split into long-term and short-term assumptions. Long-term assumptions take effect two years into the projection period, from mid-2027 onwards. Short-term assumptions are applied for mid-2026 only.

UK-level figures for mid-2025 are based on the latest estimates in our Long-term international migration, provisional: year ending June 2025 bulletin.

For mid-2026, the short-term assumptions are produced using a methodology based on analysis of historic data and assumptions about behaviour to identify the proportion of migrants who may stay by visa type, for each year after their arrival. Following the application of this, results were constrained to the latest mid-2025 provisional estimate. A different approach has been taken for Northern Ireland where we have assumed the same levels of international migration over the full projected period. Find more information on this in Section 6: International migration assumptions for Northern Ireland.

Further information on our methodology can be found in our National population projections quality and methods guide. Further information on variant projections can be found in our National population projections, variant projections: 2024-based methodology.

Latest estimates for mid-2025

International migration statistics for England, Wales and Scotland in this methodology were derived from latest provisional total UK international migration released in November 2025. These derived statistics are likely to differ from future statistics on international migration for England, Wales and Scotland.

Our data and methodology have evolved over recent releases, and we now use the latest available admin-based international migration data in the projections, including where these exist beyond the base year.

International migration assumptions are held constant from mid-2027 onwards. These are referred to as long-term assumptions. Figure 1 shows that the UK long-term assumption for net international migration is positive 230,000 per year. This is from a projected immigration of 710,100 people per year and a projected emigration of 480,100 people per year. This assumption of 230,000 net UK migration is from a 10-year average of estimated international migration from mid-2013 to mid-2021, and mid-2025. The long-term assumption is based on historic net migration; immigration and emigration assumptions were then calculated.

Figure 1 also shows the UK short-term assumption for mid-2026. The short-term assumption uses a new method detailed in Section 5: Short-term assumption setting using stay rates – UK, England, Wales, and Scotland. These run from the latest provisional estimate for mid-2025 UK net international migration of 204,000, to the start of the long-term assumption from mid-2027 onwards. We based the year in which the long-term assumptions start on our new method for setting short-term assumptions and when the short-term assumptions increased above the level of the long-term assumption.

The latest provisional estimate to mid-2025 showed net migration decreasing from a peak in 2023. However, this may not necessarily continue at the same pace or with consistency over time.

Engagement with our Migration Expert Advisory Panel (MEAP), comprising principally of academic experts in the field of international migration, highlighted considerable uncertainty with a lot of variation in expert feedback. We invited experts to provide an indication of potential central, low and high levels of migration in future years.

Responses to a questionnaire we issued gave views on future prospects for international migration to and from the UK over the next 2, 5, and 25 years from the latest provisional estimate. This took place at the end of November 2025 following our Long-term international migration, provisional: year ending June 2025 bulletin. For example:

• for net migration in 2027 the mean central estimate average was 188,000 and the range of individual estimates was 465,000

• for net migration in 2030 the mean central estimate average was 186,000 and the range of individual estimates was 400,000

• for net migration in 2050 the mean central estimate average was 244,000 and the range of individual estimates was 280,000

At the Migration Expert Advisory Panel meeting on 16 December 2025, we presented the latest provisional data and updates to previous data points; we also explained the new method in use for short-term assumption setting and held a discussion of the results and views.

Table 1 shows international net migration at the UK level and for England, Scotland, Wales, and Northern Ireland. Long-term assumptions for constituent UK countries have been developed using the historic proportion of the inflows and outflows to each UK constituent country; this leads to the UK total estimate. For Northern Ireland, 2,000 net international migration is assumed for the entire projections period. This is based on a 10-year average of years 2012 to 2021.

Find more information on assumptions for Northern Ireland in Section 6: International migration assumptions for Northern Ireland.

Long-term variant assumptions

In addition to the principal projection, we developed three variant assumptions for international migration:

• high migration

• low migration

• zero net migration

These variants show:

• what could happen to international migration over the projection period

• the resulting population projections if international migration is higher or lower than the principal assumption

Variant projections and the outcomes from these for the projected UK population are shown in our National population projections, variant projections: 2024-based methodology.

Assumptions for high migration and low migration variant projections

High and low long-term variant international migration assumptions are only based on expert advice provided through November and December 2025. This included consideration of the latest data from our Long-term international migration, provisional: year ending June 2025 bulletin.

The long-term high migration variant for the UK is positive 455,000 net migration. The low migration variant for the UK is positive 105,000 net migration. These figures are based on expert views collected before our Migration Expert Advisory Panel meeting in December 2025.

In comparison, the principal long-term migration projection is 230,000 net migration.

Assumptions for zero net migration variant projections

The zero net migration variant includes zero net international and cross-border (sometimes also known as "internal" or "within UK" migration). Zero for both is assumed from the base year onwards. This allows us to project population change in the absence of any international or cross-border migration. 

Comparing all variant assumptions

Figure 2 shows the UK-level net international migration principal assumptions, variant assumptions, and the historic time series of net migration estimates. Under principal and low migration assumptions, it is assumed that the net migration will decrease in the year to mid-2026, from the latest provisional estimate for mid-2025. It will recover to the long-term assumption in 2027.

In the high-migration variant, it is assumed that the net migration will increase in the first year of the projections from the latest provisional estimate for mid-2025, before reaching the long-term assumption in 2027.

Table 2 shows the international migration variant assumptions for the UK and its constituent countries. For all variant migration assumptions, to provide short-term assumptions for mid-2026 we scaled the difference to the high and low variant from the principal assumption. This is in line with our principal projection and the general views from our Migration Expert Advisory Panel Meetings. A different approach has been taken for Northern Ireland, where 2,000 net migration has been applied for both short-term and long-term assumptions.

Using a new method for setting short-term assumptions

Following the release of the 2022-based national population projections (NPPs), we initiated a review of potential methods for use in place of a linear interpolation for moving to the long-term assumption from the latest provisional estimate. This included expert and stakeholder feedback on the quality, value, and timeliness of prospective methods. We are grateful to those who contributed towards the review.

The 2024-based principal NPPs adopt, in the principal and variant projections, the stay‑rate method previously used in the 2022‑based migration category variant. This method uses assumptions about the type of immigration and whether those who have arrived on different types of visa stay in the UK. It calculates the stay rates (the proportion of individuals who remain in the country after a certain period) and uses this to estimate resulting outflow and net migration.

Further information on the method can be found in the University of Oxford's report Why are the latest net migration figures not a reliable guide to future trends?. This type of method has also been used by the Office for Budget Responsibility (OBR), as described in their Net migration forecast and its impact on the economy report.

This method has been developed over the last few years as an alternative for examining the potential implications for emigration and net migration that result from different types of immigration.

Important assumptions and parameters used

To develop stay rates, several important assumptions, or parameters, are needed. For the 2024-based NPPs, the results from the system are based on: 

• Home Office migrant‑journey data (2014 to 2024) to calculate stay rates

• exclusion of Temporary Workers from the stay‑rate calculation

• post-Brexit data to calculate the proportion of visas that convert into long‑term immigration

• humanitarian assumptions derived using the June 2019 to June 2025 long-term international migration data, with a 12-month adjustment speed to meet the assumption

• British nationals ̶ we assumed future net migration of negative 90,000 with emigration set to negative 180,000, and immigration to 90,000

• an assumption that EU non-visa migration reaches zero net migration over 48 months

These assumptions were informed by seeking further expert advice following the Expert Advisory Panel meeting in December 2025.

After generating results from the system, we constrained these back to the latest provisional estimate. This was done by calculating the scale of year-by-year change from the results and then applying this proportionately to the latest provisional estimate to mid-2025.

Doing this generated the short-term assumption to mid-2026, after which application of the proportionate change led to an assumption slightly higher than the long-term assumption for mid-2027; this led to the movement to the long-term assumption. This ensures a smoother transition between the short- and long-term assumption.

For the 2024-based national population projections (NPPs), a different approach has been taken to setting international migration assumptions for Northern Ireland, compared with the other parts of the UK and previous releases.

In the past, a linear interpolation has been applied to reach the long-term assumption from the latest provisional estimate. While we developed a new method which is applied at the UK-level, and when disaggregated led to the assumptions for the constituent countries, there were challenges in taking the same approach for Northern Ireland.

Specifically, it is challenging to apply the stay-rate method because Northern Ireland has a land border with Ireland. British and Irish citizens are permitted to move freely across the border because of the Common Travel Area (find more detail in Section 15: Definitions). For the 2024-based NPPs, it was not possible to adjust the UK-wide method to take this into account, specifically for Northern Ireland.

Reflecting the overall movement of international migration and our long-term assumptions, we instead set a flat assumption for Northern Ireland covering the entire projected period. No international migration data for the year to mid-2025 were available from the Northern Ireland Statistics and Research Agency (NISRA) at the point at which assumption setting was concluded; this led to the use of an assumption for the year to mid-2025.

The assumption for annual net international migration for Northern Ireland is 2,000. This corresponds with a 10-year average of past migration estimates for Northern Ireland for the period 2012 to 2021 and our exclusion of the years 2022, 2023, and 2024 from setting the long-term assumption. The resulting assumption is similar to the disaggregated UK percentage of Northern Ireland inflows, outflows and resulting net migration applied to the UK-wide provisional estimate for mid-2025.

As for the long-term assumption at the UK-level, the assumption for Northern Ireland should be treated as a long-term average around which there will be year-to-year fluctuation. Following the publication of 2024-based NPPs, we will review the assumption setting for Northern Ireland and consider whether there are further developments or innovations we can make.

Historic inflows and outflows data for England, Wales, Scotland, and Northern Ireland by single year of age and sex are used to generate an assumed profile of future inflows and outflows for assumptions. The results from this process are then applied to assumed international inflows and outflows in each year of the projections period for each constituent UK country. This approach reflects differences seen across the UK in age and sex of international inflows and outflows.

We have used migration estimates for the five-year period ending in mid-2022 to derive the single year of age and sex international immigration, emigration and resulting net migration for the assumptions in these national population projections (NPPs).

There has been substantial change in international migration over recent years. This has been reflected in the age and sex profiles of international immigration and emigration. Figure 3 shows the single year of age and sex long-term assumptions for net migration for males and females at the UK-level. The full details of the age and sex distribution of international migration assumptions in the NPPs can be found in our accompanying machine-readable dataset.

Age and sex of international migrants

We assume a fixed age and sex distribution for each UK country, which is consistent with our approach in previous NPPs. This is based on an average derived from the five years of historical international migration data to mid-2022 from the mid-year population estimates components of change for the corresponding country. We then apply this to the assumed immigration and emigration at each mid-year in the projections period.

Single year of age and sex statistics for immigration, emigration, and net migration can be found in our accompanying machine-readable datasets.

Cross-border migration is the movement of residents between the four constituent countries of the UK. Cross-border migration assumptions are set as rates calculated using 10 years of historical data (2015 to 2024). They are applied to the population of each UK country to calculate how many people are assumed to move to a different UK country for each year in the projection.

The main advantage of applying rates for cross-border migration is that migrant flows are linked to the changing size and age structure of the underlying population. This means that the projection cannot produce implausible values, like negative population stocks.

The methodology for producing cross-border migration rates in the national population projections (NPPs) is explained in more detail in our Method for incorporating cross-border migration rates into the UK NPPs report (PDF, 399KB). Cross-border migration is calculated using data from the mid-year population estimates.

Figure 4 shows estimated total international migration in England from mid-2013 to mid-2025, with projected total international migration from mid-2025 to mid-2035. Estimated net international migration reached its highest estimated level in mid-2023 at 827,200. Net international migration is projected to be 128,600 in mid-2026 and is assumed to remain at positive 211,000 from mid-2027 onwards.

Figure 5 shows the estimated total net international migration in England from mid-2013 to mid-2025, with projected total net international migration from mid-2025 to mid-2035 for the principal, high migration, low migration and zero net migration variants. For the high migration variant, total net international migration is assumed to remain at positive 417,500 from mid-2027 onwards. For the low migration variant, total net international migration is assumed to remain at positive 96,500 from mid-2027 onwards.

Figure 6 shows projected net cross-border migration for England used in the 2024-based national population projections from mid-2025 to mid-2074. Net cross-border migration is assumed to be negative throughout this projection period. The level of net cross-border migration increases from mid-2025 to mid-2040, before declining until around mid-2051. From the mid-2050s onwards, net cross-border migration is assumed to increase steadily.

Figure 7 shows estimated total international migration in Wales from mid-2013 to mid-2025, with projected total international migration from mid-2025 to mid-2035. Estimated net international migration reached its highest estimated level in mid-2023 at 27,300. Net international migration is projected to be 3,000 in mid-2026 and is assumed to remain at positive 5,500 from mid-2027 onwards.

Figure 8 shows the estimated total net international migration in Wales from mid-2013 to mid-2025, with projected total net international migration from mid-2025 to mid-2035 for the principal, high migration, low migration and zero net migration variants. For the high migration variant, total net international migration is assumed to remain at positive 11,000 from mid-2027 onwards. For the low migration variant, total net international migration is assumed to remain at positive 2,500 from mid-2027 onwards.

Figure 9 shows projected net cross-border migration for Wales used in the 2024-based national population projections from mid-2025 to mid-2074. Net cross-border migration is assumed to be positive throughout this projection period. The level of net cross-border migration decreases from mid-2025 to mid-2040, before rising until around mid-2053. From the mid-2054 onwards, net cross-border migration is assumed to decrease steadily.

Figure 10 shows estimated total international migration in Scotland from mid-2013 to mid-2025, with projected total international migration from mid-2025 to mid-2035. Estimated net international migration reached its highest estimated level in mid-2023 at 61,800. Net international migration is projected to be 4,400 in mid-2026 and is assumed to remain at positive 11,500 from mid-2027 onwards.

Figure 11 shows the estimated total net international migration in Scotland from mid-2013 to mid-2025, with projected total net international migration from mid-2025 to mid-2035 for the principal, high migration, low migration and zero net migration variants. For the high migration variant, total net international migration is assumed to remain at positive 22,500 from mid-2027 onwards. For the low migration variant, total net international migration is assumed to remain at positive 5,000 from mid-2027 onwards.

Figure 12 shows projected net cross-border migration for Scotland used in the 2024-based national population projections from mid-2025 to mid-2074. Net cross-border migration is assumed to be positive throughout this projection period. Net cross-border migration increases slightly from mid-2025 to mid-2029, before decreasing steadily from mid-2030 onwards. A brief period of relative stability is observed around the mid-2040s. After this, net cross-border migration resumes a gradual downward trend to mid-2074.

Figure 13 shows estimated total international migration in Northern Ireland from mid-2012 to mid-2025, with projected total international migration from mid-2025 to mid-2035. Estimated net international migration reached its highest estimated level in mid-2023 at 7,600. Net international migration is assumed to remain at positive 2,000 from mid-2027 onwards

Figure 14 shows the estimated total net international migration in Northern Ireland from mid-2012 to mid-2025, with projected total net international migration from mid-2025 to mid-2035 for the principal, high migration, low migration and zero net migration variants. For the high migration variant, total net international migration is assumed to remain at positive 4,000 from mid-2027 onwards. For the low migration variant, total net international migration is assumed to remain at positive 1,000 from mid-2027 onwards.

Figure 15 shows projected net cross-border migration for Northern Ireland used in the 2024-based national population projections from mid-2025 to mid-2074. Net cross-border migration is assumed to be negative throughout this projection period. The level of net cross-border migration decreases from mid-2025 to mid-2032, before increasing steadily from mid-2033 to around the mid-2050s. From the mid-2050s onwards, net cross-border migration decreases again, before increasing slightly towards mid-2074.

We held a Migration Expert Advisory Panel meeting on 16 December 2025 to gather advice and feedback on future migration; this helps us with the development of our assumptions. Experts were able to consider the implications of our Long-term international migration, provisional: year ending June 2025 bulletin ahead of the meeting. Minutes from the panel meeting can be requested by emailing pop.info@ons.gov.uk.

Following the meeting, and as part of our development of important assumptions and parameters for the stay rate method, we agreed expert data access prior to publication for quality assurance. This access was requested by the Head of Population and Household Projections at the Office for National Statistics (ONS) and approved by the ONS Statistical Head of Profession.

Asylum, refugee, and Vulnerable Persons Resettlement Schemes

Assumptions include people who migrated to the UK as refugees, or through Vulnerable Persons Resettlement Schemes, because migration estimates include this type of migration. However, the migration assumptions in the principal projection do not attempt to separately project these types of migration, because they project based on assumed levels of future migration overall.

Armed forces resettlement

Short-term assumptions no longer account for the return of UK armed forces personnel and their dependants because their return has been completed.

Common Travel Area (CTA)

A long-standing arrangement between the UK, Northern Ireland, Ireland, the Channel Islands, and the Isle of Man, permitting free movement for British and Irish citizens.

International migration in the national population projections

The national population projections (NPPs) define migration using the United Nations (UN) definition of a long-term international migrant as someone who has moved to a country other than their usual country of residence for a period of 12 months or more.

The NPP long-term migration assumptions do not include short-term international migrants under the UN definition (that is, those who move to or leave the UK for less than 12 months).

National population projections table of contents
Dataset | Released 28 April 2026 
Tools to locate the dataset tables and supporting documentation for the national population projections. Contains links to the principal and variant projections for the UK and constituent countries for 100 years ahead.