What you'll learn

• How the UK's age and sex structure has changed from 1900 to the present day.
• How the UK has moved through the Demographic Transition Model.
• Why the UK has an ageing population, and the effects and responses.
• The main 21st-century immigration flows into the UK and their social and economic impacts.

The starting point: what is population structure?

A population is the number of people living in a place. For this topic, the place is mainly the UK at the national scale, but you should also think locally: your town, ward, borough or county may be very different from the national average.

A birth rate is the number of live births per 1,000 people per year. A death rate is the number of deaths per 1,000 people per year. Natural increase happens when births are higher than deaths; natural decrease happens when deaths are higher than births.

$$natural\; change=birth\; rate-death\; rate$$

A fertility rate is the average number of children a woman is expected to have. A life expectancy is the average number of years a newborn baby is expected to live if current death rates continue.

How the UK's population structure has changed since 1900

In 1901, the UK had about 38 million people. By the early 2020s, it had around 67 million. The exact figure depends on the year and data source, but the long-term trend is clear: the UK has grown and become older.

In the early 1900s, the UK had a more youthful structure. There were many children, fewer people survived into old age, and infectious diseases were more dangerous. Today, birth rates are lower, families are smaller, healthcare is better, and many more people live into their 70s, 80s and beyond.

A population pyramid is a graph showing the age and sex structure of a population. Males are usually shown on the left, females on the right, and age groups run from youngest at the bottom to oldest at the top. The two shapes below show the main change: from a wide-based pyramid to a more rectangular, ageing structure.

The UK and the Demographic Transition Model

The Demographic Transition Model, often shortened to DTM, is a model showing how birth rates, death rates and total population tend to change as a country develops economically and socially.

The UK was one of the first countries to move through the DTM because it industrialised early. Before industrialisation, both birth and death rates were high. During the Industrial Revolution and after, death rates fell because of improvements in food supply, sanitation, clean water and medicine. Birth rates later fell as contraception, education, urban living, changing roles of women and the cost of raising children reduced family size.

Around 1900, the UK was in late Stage 3 or moving towards Stage 4: birth rates had started to fall, death rates were already lower, and population was still increasing. In the mid to late 20th century, the UK was mainly Stage 4, with both birth and death rates low. Today, the UK is usually seen as Stage 4, with possible Stage 5 tendencies because fertility is low and the population is ageing.

Why is the UK ageing?

An ageing population is a population where the proportion of older people is increasing. In the UK, this mainly means a growing share of people aged 65 and over.

The main causes are:

• Longer life expectancy: better healthcare, vaccinations, safer work, improved diets, clean water and better housing mean more people survive into old age.
• Lower fertility: many people have fewer children due to contraception, later marriage, higher housing and childcare costs, women staying longer in education and work, and changing social attitudes.
• The baby boom generation ageing: people born after the Second World War are now reaching older age groups.
• Local migration patterns: some younger adults move to cities for university and jobs, while some older people move to coastal or rural retirement areas such as parts of Devon, Dorset and Norfolk.

A dependent population is the part of the population often assumed to rely more on the working-age population. At GCSE, this is usually children and older people. The old-age dependency ratio compares older people with the working-age population.

$$old-age\; dependency\; ratio=\frac{population\; aged\; 65\; and\; over}{population\; aged\; 16\; to\; 64}\times 100$$

Effects of an ageing population

At the national scale, ageing can increase pressure on the NHS, adult social care and the State Pension. More older people may mean higher public spending, and a smaller proportion of working-age people may mean fewer taxpayers per pensioner.

There can also be labour shortages if many workers retire and not enough younger workers replace them. This is important in sectors such as healthcare, care work, construction and transport.

But ageing is not only negative. Older people contribute through paid work, volunteering, family care and spending. The grey pound means the spending power of older people, which supports businesses such as tourism, leisure, healthcare and home adaptations.

At the local scale, impacts vary. A coastal town with many retired residents may need more GP surgeries, accessible buses, care homes and adapted housing. A university city or inner London borough may have a younger age structure and different priorities, such as rental housing and schools.

Responses to an ageing population

The UK has several possible responses:

• Raising the State Pension age so people work for longer before receiving the state pension.
• Encouraging later-life work, including flexible hours, retraining and anti-age discrimination policies.
• Improving health prevention, such as screening, exercise schemes and support for healthy lifestyles.
• Investing in social care, including care workers, home adaptations, telecare and supported living.
• Supporting families, for example through childcare help and parental leave, which may reduce barriers to having children.
• Managing migration, because working-age migrants can help fill labour shortages, especially in health, social care, agriculture, hospitality and construction.

21st-century immigration into the UK

Migration means the movement of people from one place to another. Immigration means people moving into a country. Emigration means people leaving a country. Net migration is immigration minus emigration.

A migration flow is a movement of people from one place to another over a period of time. In the 21st century, important flows into the UK have included:

• European Union migration, especially after the 2004 EU enlargement, when many people moved from countries such as Poland and Lithuania. Later flows also included Romania and Bulgaria. Brexit changed the system, with less free movement from the EU.
• Commonwealth and global work migration, including people from India, Pakistan, Bangladesh, Nigeria and other countries, often linked to jobs, family connections, healthcare, business and education.
• International students, with many coming from countries such as China, India and Nigeria to UK universities.
• Humanitarian flows, including refugees and people arriving through schemes linked to Syria, Afghanistan, Ukraine and Hong Kong.

Many immigrants are young adults, so immigration can increase the working-age population and slightly reduce the speed of ageing. However, migrants also age over time, so migration is not a complete solution to ageing.

Impacts of immigration on the UK

Economic impacts can be positive. Immigration can fill labour shortages, increase tax revenue, support universities through tuition fees, and bring enterprise and skills. The NHS and care sector have long relied on international workers.

There can also be challenges. Rapid population growth can add pressure to housing, schools, GP services and transport, especially if local funding and planning do not keep up. In some low-paid sectors, there may be concerns about job competition or wages, although impacts vary by place and occupation.

Social impacts include greater cultural diversity, new languages, religions, food, music and community organisations. Cities such as London, Birmingham, Manchester and Leicester show this clearly. London is a major global migration gateway, with a very high proportion of residents born outside the UK.

Locally, the effects can be more concentrated. For example, parts of Lincolnshire, including Boston, experienced rapid change linked to Eastern European workers in agriculture and food processing. This brought labour supply for local businesses, but also increased demand for translation, school places, rental housing and community integration.

Using local data and fieldwork thinking

Population change is not evenly spread. Nationally, the UK is ageing, but locally, patterns differ. Inner-city areas and university towns often have younger populations. Coastal and rural areas often have older populations. London has high international migration, while some smaller towns experience more selective flows linked to particular industries.

You can investigate this using Census 2021 data, local authority profiles or choropleth maps showing over-65s, average age or people born outside the UK. In fieldwork-style thinking, you could compare a local high street with census data: care homes, mobility aids shops, schools, nurseries, language services and places of worship can all give clues about population structure.