Alongside its principal projection for the UK population, the Office for National Statistics (ONS) has published a range of scenarios showing how the figures would change with different assumptions about factors such as migration and life expectancy.
Under the principal projection, the UK population rises from 67.6 million in mid-2022 to 72.5 million in mid-2032, reaching 76.6 million by mid-2047.
This assumes net migration will settle at 340,000 per year from 2028 onwards.
If it settled at a higher level of 525,000 per year, however, the projection changes to suggest the UK population climbs to 73.8 million by mid-2032 rather than 72.5 million, and then 81.4 million in 2047 instead of 76.6 million.
But if it settled at lower level of 120,000 per year, the projection changes again, this time suggesting the UK population climbs to only 71.0 million in 2032, then actually falls slightly to 70.8 million by 2047.
Use our new UK population projection explorer to adjust factors such as life expectancy, average children per woman and net migration to see what impact each could have on the future population
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— Office for National Statistics (ONS) (@ONS) January 28, 2025
Another variable is fertility.
The ONS uses a measure of fertility called the total fertility rate.
This is the average number of live children a group of women would have if they experienced the age-specific fertility rates throughout their childbearing life.
The ONS principal population projection assumes a total fertility rate of 1.48 children in mid-2022, falling to 1.41 children by 2032 and then climbing to 1.45 children by 2047.
Under a scenario with a lower fertility rate (1.25 children by 2047), the UK population is projected to increase more slowly, reaching 71.9 million in mid-2032 rather than 72.5 million under the principal projection, and 74.5 million in mid-2047 rather than 76.6 million.
A higher fertility rate (1.65 children by 2047) changes the projection again, to give a population of 73.0 million in 2032 and 78.4 million in 2047.
Different assumptions about life expectancy alter the projection, but only slightly.
An improvement rate of 1.5% in the current life expectancy of males and females aged 0 to 90 results in a population projection of 72.5 million by 2032 and 76.8 million by 2042, while a lower improvement rate of 0.5% gives a projection of 72.5 million by 2032 and 76.2 million by 2042.
The ONS has also produced two projections based on groups of variables: a “high population” projection, where fertility, life expectancy and migration are all higher than the principal projection; and a “low population” projection, where those same three factors are all lower.
Under the “high” projection, the population climbs to 74.3 million by mid-2032 (compared with 72.5 million under the principal projection) and then reaches 83.6 million by mid-2047 (compared with 76.6 million).
Under the “low” projection, the population reaches only 70.4 million by 2032 and then drops to 68.6 million by 2047.
“Variant projections are of importance where we continue to see uncertainty and complexity in population change,” according to James Robards, ONS head of population and household projections.
“Over recent years fertility has continued to fall to historically low levels, international migration has been at very high levels and mortality has continued to change after the Covid-19 pandemic and from the early 2010s, when we first started to see a slowdown in improvement in life expectancy.
“This all makes setting assumptions more challenging and uncertain than it has been in the past.”
A wide range of variant projections allow people to see “the potential implications of higher and lower drivers of population change,” he added.
“These give insights into what a single type of population change (e.g. lower mortality) and multiple trends (e.g. lower mortality, lower fertility and higher mortality) might mean for the future population.”
