The population of the UK is projected to grow from an estimated 67.0 million in mid-2021 to 73.7 million by mid-2036, according to new figures from the Office for National Statistics (ONS).
This represents an increase of around 6.6 million, or 9.9%.
Long-term international net migration – the difference between the number of people entering the country and leaving – is projected to account for 6.1 million of the increase, with the remainder coming from a higher number of births than deaths.
All the figures are projections, not predictions or forecasts, because they are based on current and past trends.
The actual levels of future migration and population may be higher or lower, and will be “affected by policy changes as well as the impact of as yet unknown migrant behaviour patterns”, the ONS said.
The new projections assume that net migration will fall over the next few years from a peak of around 670,000 in the 12 months to June 2023, before settling at 315,000 from 2028 onwards.
Over the 15 years from mid-2021 to mid-2036 it is projected that 10.8 million people will be born, 10.3 million will die, 13.7 million will move long term to the UK, while 7.6 million people will emigrate.
The new projections point to “the likelihood of higher levels of international migration over the long term” than in previous estimates, said ONS head of population and household projections James Robards.
“Expert views and the latest data covering the last 10 years has led us to develop a long-term net migration assumption of 315,000 each year from year ending mid-2028 onwards”, he continued.
“It is important to recognise that there is uncertainty in the provisional international migration estimates. Future migration will be affected by policy changes as well as the impact of as yet unknown migrant behavioural patterns in the future.
“Put simply, if migration comes down so will future projections.
“If net international migration were to be, say, 20% higher than our long-term assumption, then it would be 379,000 per year. If it were to be 20% lower than our assumption, then it would be 253,000 per year.
“That is why we call these projections and not forecasts. There is uncertainty and these differences would affect the total size of the population accordingly.”
The latest projections suggest the UK population could hit 70 million by mid-2026 – a decade sooner than in figures published in 2022, which projected a date of mid-2036.
They also suggest the size of the UK population aged 85 and over could grow in the next 15 years from 1.6 million (2.5% of the total population) to 2.6 million (3.5%).
The demographic mix of the population is projected to continue tilting more towards older age groups.
People aged 75 and over could account for one in 10 of the total population by 2029 and one in nine by 2037 – the same year that people of pension age are projected to account for one in five.
The total projected increase in the UK population over the next 25 years is proportionately less than that over the past 25 years.
From mid-1996 to mid-2021, the population grew by 8.9 million (15.3%), while from mid-2021 to mid-2046 it is projected to grow by 9.5 million (14.2%).
The ONS said it will continue to develop its population figures during 2024, taking into account the latest data on international migration, and will update its projections towards the end of the year.