Understanding the size and characteristics of a country’s population is vital when it comes to planning and delivering services like education, transport and healthcare.

Population change occurs as a result of births, deaths and net migration (the difference between immigration and emigration). These factors may also affect the age and sex structure of the population.

Part of a series of UK Perspectives providing an overview of key aspects of the nation over the last 4 decades, this article presents some key statistics relating to the changing UK population.

1. The UK population has grown by 8.4 million since 1975

Mid-year population estimates for the UK, 1975 to 2014

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Since 1975, the UK population has grown by 8.4 million people (14.9%), to 64.6 million in 2014. Around half of this growth has occurred since 2005, due to an increase in the number of births and an increase in net inward migration through the 2000s.

2. What is driving UK population growth?

Factors driving UK population change, mid-year estimates, 1992 to 20141

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Between 1999 and 2011 net migration was the main component of population change in the UK. However, births have exceeded deaths throughout the last two decades and since 2002 there has been a marked increase in the number of births, with 2012 having the highest number since 1972. The increase in the number of births has been driven both by the immigration of women who are currently of childbearing age and by rising fertility among UK-born women.

In the year to mid-2014, the population increased by 491,100. Of this increase 54% (264,900) was due to net international migration which is the difference between international immigration and international emigration during the year. The remaining 46% (226,200) was due to natural change or the difference between births and deaths.

Current and past international migration also has indirect effects on the size of the population as it changes the number of births and deaths in the UK. For example, statistics on the number of births by the country of birth of the mother show that 200,023 live births (26% of total live births) in the UK in 2014 were to mothers born outside the UK.

3. The UK’s ageing population: life expectancy predicted to rise steadily for men and women

Cohort life expectancy at birth, UK, 1980 to 2039

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A boy born in the UK in 1980 could expect to live 84.4 years on average. For a boy born today (2016) the figure is 90.6 years and, based on current assumptions, by 2039 it is projected to be 93.9 years.

Similarly, a girl born in 1980 could expect to live 88.0 years on average. For a girl born today (2016) the figure is 93.5 years and, based on current assumptions, by 2039 it is projected to be 96.5 years.

With life expectancy increasing, the UK’s population will age. This will affect a number of policy areas, including pensions and the health service – particularly because healthy life expectancy is not increasing as quickly.

4. Changes to state pension age impacts the old age dependency ratio

The old age dependency ratio (OADR) measures the number of people of State Pension Age (SPA) and over for every 1,000 people of working age (16 to SPA). The OADR provides an idea of the relationship between working and pensioner populations.

Old age dependency ratio (OADR), UK, 1980 to 20392^^3^^4

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The OADR was steady at around 300 from the 1980s to 2006, but rose in 2007-09 as women born in the post-World War II baby boom reached SPA. In the absence of any increases to SPA, it would reach 487 by 2039; but, as a result of planned SPA increases taking place between 2010 and 2046 under current legislation, it is expected that – for every 1,000 people of working age in 2039 – there will be 370 people of SPA.

The increase in the OADR means there will be fewer people of working age to support a larger population over SPA.

5. The number of UK residents aged 90 and over has almost tripled since the early 1980s

UK residents aged 90 and over per 100,000 UK residents, 1983 to 2014

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Although the 90 and over group account for only a very small proportion of the UK population (0.9% in 2014), the size of this age group relative to the rest has increased over time. This illustrates the UK’s ageing population.

Conclusion: An increasing and ageing population

The UK population is both increasing and ageing. Current projections show this pattern is set to continue, reaching a projected 74.3 million by 2039.

That’s an increase of 9.2 million (14%) compared with 2015 as a result of births minus deaths, plus net migration.

While a larger population increases the size and productive capacity of the workforce, it also increases demand for education, healthcare and housing.

Meanwhile, longer life expectancy is resulting in a growing older population. People working longer will increase the size of the labour force, but there will also be further pressure on services. The old age dependency ratio is expected to increase in future years, although planned changes to the State Pension Age will slow this increase.

Please see related links for other relevant data sources and analysis.

For more information, please contact: digitalcontent@ons.gov.uk


  1. Net international migration includes other small population changes, such as changes to armed forces between UK and overseas.
  2. This chart is an update to the OADR chart found in Pension Trends, Chapter 2: Population change (2012 edition). Here the OADR from 1980 to 2014 is based on 2014 mid-year estimates. From 2015, the OADR uses 2014-based mid-year projections.
  3. Population projections are uncertain and become increasingly uncertain the further they are carried forward in time. They do not attempt to predict the impact that future government policies, changing economic circumstances or other factors might have on demographic behaviour.
  4. SPA changes take into account current legislation but do not take into account proposed future changes to the state pension age that are yet to become law. For the purposes of this analysis, the changes are applied to the UK population, although it should be noted that pensions in Northern Ireland are a devolved matter.