2024-based population projections: a GAD technical bulletin
Published 21 August 2026
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Introduction
The 2024-based national population projections (NPPs) from the Office for National Statistics (ONS) provide an indication of future developments of the UK and its constituent countries’ population size and age structure. The NPPs were published in April 2026. This bulletin summarises some of the key findings at the UK level and focuses on the mortality assumptions and results which are most relevant to GAD’s work.
Overall results
The main results include:
- An increasing population - the UK population is projected to increase from an estimated 69.3 million in mid-2024 to a peak of 72.5 million in mid-2054. After this date the UK population is projected to decrease.
- Net international migration remains the only source of expected population growth - though at a lower level than in the previous 2022-based NPPs. There are expected to be a lower number of births than deaths over the projection period.
- An ageing population - the number of people aged 85 years and over is projected to double in the next 25 years, from 1.8 million in mid-2024 to 3.6 million by mid-2049. The number of working-age people is expected to increase by around 5% over the same period.
- An increased old-age-dependency ratio - for every 1,000 people of working age, there will be 329 people of pensionable age by mid-2049, up from 280 in mid-2024
Figure 1: Age structure of the UK population, mid-2024 and mid-2034
Source: ONS, National population projections
Interactive population pyramids are available on the ONS website.
Figure 2: UK principal population projection to mid-2049
Source: ONS, National population projections
The assumptions for the 2024-based NPPs project fewer births, less net international migration and fewer deaths than the assumptions underlying the previous 2022-based NPPs. This leads to a lower projected total population for the UK in mid-2049 under the 2024-based NPPs of 72.4 million compared to 75.9 million under the 2022-based NPPs.
Data and assumptions
ONS produce a ‘principal’ projection based on a set of long-term assumptions considered to best reflect patterns of future fertility, mortality, and net migration based on recent data. These are derived from analysis of past trends and through consultation with independent experts in each of these fields.
It is important that projections are not viewed as predictions or forecasts, but as an indication of the future based on observed demographic trends and the assumptions adopted.
This release is based upon the 2024 mid-year estimate for the UK population.
Mortality assumptions
To project the number of people at each age in the future, it is key to work out how long people are expected to live. Historically life expectancy in the UK has generally improved over time (albeit at a slower rate in recent years), so it is important to consider how these improvements will continue in the future.
Data from the UK mid-year population estimates and annual calendar year deaths from 1975 to 2024 were used within a mathematical model to project future mortality rates and improvement rates by age and sex. The improvements in mortality rates were set to converge to a ‘long-term rate of improvement’ (LTR) in the 25th year of the projections (2049) and remain constant thereafter.
Assumptions used in the model for mortality improvements are based on an analysis of mortality data as well as advice from the external NPP Mortality Expert Advisory Panel. The Expert Panel advise on several areas, in particular the level and trend of improvements in mortality rates in the short and medium-term, the LTR, differences between England, Scotland, Wales and Northern Ireland, and other technical aspects of the mortality model.
The ONS has maintained the LTR of 1.1% per annum for ages 90 years and under. This was unchanged from the 2022-based projections (having been 1.2% for projections between 2010 and 2021). At older ages, the LTR decreases linearly from 1.1% at age 90 to 0% at age 110, and is set at 0% for ages 110 years and over.
Impact on life expectancy
Life expectancies are projected to continue increasing over time under the 2024-based projections, reflecting assumed future improvements in mortality.
The overall effect is that the 2024-based cohort life expectancy projections (which allow for future mortality improvements) are very similar to the 2022-based projections, with differences of less than 0.1 years for both males and females at the ages shown below.
Figure 3: Sample cohort life expectancies in 2026, UK
| 2024-based projections (years) | 2022-based projections (years) | |
|---|---|---|
| At birth | ||
| Males | 87.2 | 87.2 |
| Females | 90.5 | 90.4 |
| At age 65 | ||
| Males | 20.2 | 20.1 |
| Females | 22.9 | 22.8 |
Source: ONS, expectation of life, principal projection, UK
The chart below shows the principal projections of period life expectancy at birth for males and females (which are based on mortality rates in the year of interest and do not allow for future mortality improvements beyond that year), comparing successive projections from the 2014-based to the 2024-based projections. For both sexes, the 2024‑based projections are similar to the 2022‑based projections. However, these are lower than the 2014-based, 2016-based, 2018-based, and 2020-based (for males) projections, although life expectancy is still projected to increase over time. The lower projected life expectancies reflect the increasing number of recent years with lower improvements and a slightly lower projection of future improvements compared to earlier projections.
Figure 4: Principal period life expectancy at birth: changes between 2014-based and 2024-based projections, UK
Source: ONS, National population projections, mortality assumptions
Other assumptions - migration and fertility
Net international migration is projected to increase the UK population, but at a lower rate than the 2022-based projections. The average annual net international migration assumption is 230,000, compared to 340,000 assumed in the 2022-based projections. This reflects the sharp decrease in net migration from its peak in 2023, as well as expert advice.
The assumed UK total fertility rate (TFR) is 1.38 children per woman by 2029, rising in the long-term to 1.42 children per woman by 2049. This long-term assumption is slightly lower than the assumption of 1.45 children per woman adopted for the 2022-based projections. It is also significantly lower than the replacement fertility rate of 2.075 - the level of fertility required for the population to replace itself in size in the long term, in the absence of migration.
The key assumptions relating to the principal projection are summarised in the following table:
Figure 5: UK long-term assumptions for the 2024-based national population projections compared with 2022-based
| 2022-based | 2024-based | |
|---|---|---|
| Net annual long-term international migration (mid-2027 onwards) | 340,000 | 230,000 |
| Long-term average number of children per woman | 1.45 | 1.42 |
| Life expectancy at birth, females, 2049 (years) | 85.8 | 85.9 |
| Life expectancy at birth, males, 2049 (years) | 82.2 | 82.4 |
Source: ONS, National population projections
Variant projections
For the 2024-based NPPs, ONS has published 13 variant projections alongside the principal projection. These are based on alternative assumptions of fertility, mortality, and migration compared with the principal projection. They provide an indication of uncertainty in, and the outcomes of, alternative assumptions, however they should not be interpreted as upper or lower limits of future demographic behaviour. Variant scenarios relating solely to life expectancy are the high life expectancy, low life expectancy and no long-term mortality improvement variants.
An interactive population projection explorer produced by the ONS, helps illustrate the effect of different assumptions on the UK’s projected population up to 50 years in the future.
How are the NPPs used at GAD?
Assumptions for how long people are going to live are key in GAD’s work relating to pension schemes. The assumptions underlying the most recent NPPs are usually used in the valuations, accounts and factors for public service pension schemes. They are also used for some of the other schemes we advise as well as in key policy work such as the State Pension age review.
Future fertility and migration rates impact other areas of our work that relate to the working age population and the latest NPPs are usually used. Examples of such work are the projection of contribution income and benefit spend for our reviews of the National Insurance Fund.
The use of NPPs ensures consistent assumptions are used across government for projecting future public finances.
If you would like to discuss the NPPs in more detail or have any questions about the implications for our work for you, please get in touch with your usual GAD contact or email: enquiries@gad.gov.uk.