According to Office for National Statistics projections released today, by mid-2039 more than 1 in 12 of the population will be 80 or over. The number of people of pensionable age will rise from 12.4m now to 16.5m by 2039.
The ONS projects that the UK population will reach 70 million by mid-2027, more than 5m higher than 2014.
The statistics body has assumed that net migration will account for 51% of the projected increase over the next 25 years, with a natural increase in population (more births than deaths) accounting for the remaining 49% of growth.
The population is projected to continue ageing, with the average (median) age rising from 40 in 2014 to 40.9 in mid-2024 and 42.9 by mid-2039.
The table shows the different projections for different parts of the UK. These show that England’s population is predicted to rise by 9m by 2039. Scotland will see an extra 400,000 people over this period, Wales 200,000 and Northern Ireland the same number.
Over the full 25 year period of the projection, the UK population is projected to increase by 15.0% to 74.3 million by mid-2039, with an annual average growth rate of 0.6%.
Despite increases to State Pension Age under existing legislation ONS says the number of people of State Pension Age and over is projected to increase by 32.7 per cent from 12.4 million in mid-2014 to 16.5 million by mid-2039. This reflects the higher number of people who were born in the 1960s "baby boom" reaching State Pension Age.
The number of people of pensionable age for every thousand people of working age (termed the "Old Age Dependency Ratio") was 310 in 2014. This is projected to fall to 284 in 2020 as a result of changes in the State Pension Age but then rise to 370 in 2039.
The number of people aged 75 and over is projected to rise by 89.3%, to 9.9 million by mid-2039. The number of people aged 85 and over is projected to more than double to 3.6 million by mid-2039 and the number of centenarians is projected to rise nearly 6 fold, from 14,000 at mid-2014 to 83,000 at mid-2039.
Guy Goodwin, ONS Director, Social and Analysis, said: "Today’s population projections show a growing and ageing population. Growth will be at a faster rate than we have seen previously, largely due to the direct impact of international migration and the indirect impact of immigration.
“Despite this, the population will also be older as those born shortly after World War Two and during the 1960s "baby boom" reach the oldest and pensionable ages respectively. Today's figures are used to inform policies, such as on pensions, migration and care, and for the planning of housing and services.
“It is important to remember that these are not predictions or forecasts, but estimates based on current trends and input from some of the UK’s top demographic experts"