The UK population has grown by over 8 million people since the start of the century, but the types of people making up this growth have drastically changed. Between 2001 and 2021/2022, the total population increased from approximately 59.1 million to 67.3 million. By examining a population pyramid, we can describe this demographic shift step-by-step. First, modern pyramids show a narrowing base compared to 2001, which represents a declining birth rate and fewer children in the population. Next, there is a widening top (often called a thicker apex); this illustrates an ageing population driven by higher life expectancy, which now stands at around 79.4 years for males and 83.1 years for females. Finally, there are distinct middle bulges in the structure, most notably in the 45–55 age range (historical "baby boomers") and the 20s–30s bracket (driven largely by inward migration).
Geographical variations mean that population structures look very different depending on where you are in the UK. Major cities like London have highly youthful pyramids with massive bulges in the 25–35 age range due to international and internal migration. In contrast, coastal areas like Dorset have "top-heavy" structures caused by older people migrating there for retirement.
Every time you hear about population growth in the news, it is almost entirely driven by people moving into the country rather than more babies being born. Since 1999, net migration has been the primary engine of UK population growth, accounting for 65% of all growth between 2004 and 2023. In the year ending June 2023, net migration hit a record high of 906,000. Meanwhile, natural increase has steadily declined since 2011. In a historic shift in 2023, the UK actually experienced a natural decrease, meaning deaths officially outnumbered births (excluding the pandemic period).
Migration also heavily influences birth statistics. The Total Fertility Rate (TFR) in the UK dropped to around 1.54–1.58 by 2021, which is well below the replacement level of 2.1. However, the TFR for non-UK-born women is significantly higher (2.03) than for UK-born women (1.54), meaning migration helps to sustain the country's birth numbers.
The formulas for calculating population change are:
1. Natural Rate of Change (Per 1,000 people) The UK has a birth rate of approx. 12 per 1,000 and a death rate of approx. 9 per 1,000. Calculate the natural rate of change.
2. Total Natural Change and Net Migration (Absolute numbers) In a given year, a UK city recorded 14,500 births and 15,200 deaths. During the same period, 38,000 immigrants arrived and 12,000 emigrants left. Calculate the total natural change and net migration.
Understanding the history of a country's birth and death rates explains why modern societies face complex challenges like funding healthcare and pensions. The Demographic Transition Model (DTM) is a framework that plots how these rates change over time as a country develops. The UK is officially in Stage 4 (Low Fluctuating), where both birth and death rates are low and stable, though it is increasingly showing characteristics of Stage 5 (Natural Decrease) due to its ageing population.
This position on the model is caused by specific social and medical advancements. The birth rate is extremely low (around 12 per 1,000) because women are increasingly prioritising higher education and careers over early motherhood, pushing the average maternal age at first birth to 30.9 years. This is combined with the widespread social acceptance and availability of contraception. Simultaneously, the death rate remains low (around 9 per 1,000) because of universal access to advanced healthcare through the NHS, comprehensive vaccination programmes, and medical breakthroughs in treating "diseases of affluence" such as cancer and heart disease.
The proportion of the UK population aged 65 and over currently sits at 18–19% and is projected to reach 25–26% by 2050. This demographic shift places intense pressure on the dependency ratio, which measures the balance between dependents (children and the elderly) and the working-age population.
This creates significant economic and social impacts. Economically, the government faces a smaller tax-paying workforce having to fund soaring State Pension costs, although businesses can benefit from the "silver surfer" economy as healthy retirees spend money on leisure and tourism. Socially, there is immense pressure on the NHS and social care systems because elderly patients require more frequent and longer hospital stays. On the positive side, elderly people contribute massive social value by providing free childcare as grandparents and volunteering in local charities.
The dependency ratio is calculated using this formula:
A coastal region in the UK has 12,000 children (aged 0–14), 28,000 elderly residents (aged 65+), and 50,000 people of working age (15–64). Calculate the dependency ratio.
Step 1: Identify the values for the formula.
Step 2: Substitute into the equation.
Step 3: Calculate.
To manage this rising dependency ratio, the UK government has introduced strategies such as gradually raising the State Pension age from 65 to 68 and encouraging the immigration of working-age adults to boost the tax base.
Students often assume the UK is firmly and only in Stage 4 of the DTM. To access top marks, you must mention that it is increasingly showing Stage 5 characteristics due to its natural decrease in 2023.
EXAM TECHNIQUE: Be careful with the term 'Natural Change'. If given rates (per 1,000), use the Natural Rate of Change formula. If given absolute numbers (totals), use the Total Natural Change formula. Never mix the two!
When asked to 'describe the structure' of a population pyramid, examiners expect specific geographical terminology: use 'narrowing base' for falling birth rates and 'widening apex' or 'thicker top' for increased life expectancy.
Remember a major limitation of the Demographic Transition Model: it does not account for migration, which is currently the main driver of the UK's population growth.
In 6-mark or 8-mark questions discussing an ageing population, always clearly categorise your points into social impacts (e.g., NHS pressure) and economic impacts (e.g., pension costs) to structure your answer perfectly.
Population pyramid
A bar graph showing the population's structure, divided by age brackets and gender.
Birth rate
The number of live births per 1,000 people in a population per year.
Ageing population
A population where the median age is rising and the proportion of elderly people (aged 65+) is increasing.
Net migration
The difference between the number of people entering a country (immigrants) and the number of people leaving (emigrants).
Natural increase
When the birth rate is higher than the death rate, resulting in population growth. Can be calculated as a total (Births - Deaths) or a rate (Birth Rate - Death Rate).
Natural decrease
When the death rate is higher than the birth rate, resulting in population decline. In 2023, the UK experienced its first natural decrease in decades.
Natural Rate of Change
The difference between the birth rate and the death rate, usually expressed per 1,000 people or as a percentage.
Total Fertility Rate (TFR)
The average number of children born to a woman during her lifetime.
Replacement level
The Total Fertility Rate required to maintain a population size without migration, typically 2.1.
Demographic Transition Model (DTM)
A model that plots changes in a country's birth rates and death rates over time as it develops economically.
Stage 4
The stage of the DTM characterised by low, fluctuating birth and death rates, leading to a high but stable total population.
Stage 5
The theoretical final stage of the DTM where the death rate slightly exceeds the birth rate due to an ageing population, causing natural decrease.
Death rate
The number of deaths per 1,000 people in a population per year.
Dependency ratio
The ratio of dependent people (aged 0–14 and 65+) to the working-age population (15–64).
Working-age population
Individuals aged 15–64 who are typically in the labour force and pay income tax.
Put your knowledge into practice — try past paper questions for Geography B
Population pyramid
A bar graph showing the population's structure, divided by age brackets and gender.
Birth rate
The number of live births per 1,000 people in a population per year.
Ageing population
A population where the median age is rising and the proportion of elderly people (aged 65+) is increasing.
Net migration
The difference between the number of people entering a country (immigrants) and the number of people leaving (emigrants).
Natural increase
When the birth rate is higher than the death rate, resulting in population growth. Can be calculated as a total (Births - Deaths) or a rate (Birth Rate - Death Rate).
Natural decrease
When the death rate is higher than the birth rate, resulting in population decline. In 2023, the UK experienced its first natural decrease in decades.
Natural Rate of Change
The difference between the birth rate and the death rate, usually expressed per 1,000 people or as a percentage.
Total Fertility Rate (TFR)
The average number of children born to a woman during her lifetime.
Replacement level
The Total Fertility Rate required to maintain a population size without migration, typically 2.1.
Demographic Transition Model (DTM)
A model that plots changes in a country's birth rates and death rates over time as it develops economically.
Stage 4
The stage of the DTM characterised by low, fluctuating birth and death rates, leading to a high but stable total population.
Stage 5
The theoretical final stage of the DTM where the death rate slightly exceeds the birth rate due to an ageing population, causing natural decrease.
Death rate
The number of deaths per 1,000 people in a population per year.
Dependency ratio
The ratio of dependent people (aged 0–14 and 65+) to the working-age population (15–64).
Working-age population
Individuals aged 15–64 who are typically in the labour force and pay income tax.