Population | IGCSE Class 10 Economics Notes

This note covers the factors that affect population growth, including the birth rate, the death rate, immigration, emigration and net migration. It explains why birth rates, death rates and net migration vary between countries, and how changes in the size and structure of a population affect a country. It also covers the concept of an optimum population, the effects of population increase and decrease, changes in the age and gender distribution, and how to interpret a population pyramid.

What factors affect population growth?

A country's population is the total number of people living in it. Population size changes from year to year because of three factors: the birth rate, the death rate and net migration. If births and immigrants exceed deaths and emigrants, population grows; if the reverse is true, population falls.

Population growth rate = Birth rate − Death rate + Net migration rate

This formula brings together the natural change in population (births minus deaths) and the change caused by people moving into and out of the country.

Each of the three components can move independently: a country can have a falling birth rate but a rising population if net migration is strongly positive, or a rising birth rate but a falling population if emigration is very high.

The natural increase of a population is the birth rate minus the death rate, and it is positive when more people are born than die. Net migration is then added to natural increase to give the overall rate of population growth.

Population growth is measured as a rate per 1000 of the population, so that countries of very different sizes can be compared fairly. A growth rate of 4 per 1000 means that the population rises by 4 people for every 1000 already living there in that year.

Population growth can be positive or negative. A country whose deaths and emigrants together exceed its births and immigrants has a negative growth rate, and its population shrinks.

What is the birth rate and how is it measured?

Definition: Birth rate. The number of live births per 1000 of the population in a year.

Birth rate = (Live births ÷ Population) × 1000

The birth rate is usually expressed as a rate per thousand rather than as a simple total, because this allows countries of very different sizes to be compared fairly.

A country with 10 million people and a country with 100 million people can be compared directly once their births are both converted into a rate per 1000 of the population, rather than left as raw totals that depend heavily on the size of the population to begin with.

A high birth rate on its own raises population growth only if the death rate and net migration do not offset it.

Governments and statistical agencies usually collect birth figures from official registrations of live births, and the resulting rate is often described as the crude birth rate, because it takes no account of the age or gender structure of the population producing it.

The birth rate is one of the three components of population growth. A country with a high birth rate and a low death rate will usually have a rapidly growing and young population, while a country with a low birth rate will grow slowly unless net migration is strongly positive.

What is the death rate and how is it measured?

Definition: Death rate. The number of deaths per 1000 of the population in a year.

Death rate = (Deaths ÷ Population) × 1000

Like the birth rate, the death rate is expressed per thousand so that countries of different population sizes can be compared on equal terms, rather than comparing raw totals of deaths that would automatically be larger in a more populous country.

It is sometimes called the crude death rate, because it takes no account of the age structure of the population producing it: a country with a larger share of elderly people will tend to show a higher crude death rate than a country with mostly young people, even where healthcare in both countries is equally good, simply because older people are statistically more likely to die in any given year.

A falling death rate, with an unchanged birth rate, increases the rate of population growth, because fewer people are dying relative to the number being born, so the natural increase in population (births minus deaths) becomes larger.

Death figures are usually collected from official death registrations kept by government agencies, and changes in the death rate over time are often used as a broad indicator of a country's level of healthcare, nutrition, sanitation and overall living standards, with a steadily falling death rate generally taken as a sign of economic development.

The death rate is the second component of population growth. Together with the birth rate it determines the natural increase of a population, before migration is taken into account.

What are immigration, emigration and net migration?

Definition: Net migration. The difference between the number of people entering a country (immigrants) and the number leaving it (emigrants) in a given period.

Immigration is the movement of people into a country to live there, while emigration is the movement of people out of a country to live elsewhere.

If immigration exceeds emigration, net migration is positive and adds to population growth; if emigration exceeds immigration, net migration is negative and reduces population growth.

Net migration is usually expressed as a rate per 1000 of the population, in the same way as the birth rate and death rate, so that migration flows can be compared fairly between countries of different sizes.

Net migration = Immigration − Emigration

Migration can change the age structure, gender balance and skills profile of a population quite quickly, because migrants are often of working age and may be disproportionately male or female depending on the type of work available, whereas changes in birth and death rates affect population size and structure much more gradually, over many years rather than months.

A country receiving large numbers of working-age immigrants may see its workforce grow faster than its total population, while a country losing working-age emigrants may see its dependency ratio rise even if its birth and death rates have not changed at all.

Net migration is the third component of population growth. Unlike births and deaths, it can change a country's population size sharply within a single year, because large numbers of people can move in or out over a short period.

Why do birth rates differ between countries?

Birth rates tend to be higher in low-income countries and lower in high-income countries, though this is a general pattern rather than a rule that applies to every country. Several factors explain the difference.

1. Access to healthcare and family planning: countries with widespread access to contraception tend to have lower birth rates, as couples can plan family size more easily.
2. The level of education, especially of women: higher female education is associated with women entering paid work and having fewer children later in life, lowering the birth rate.
3. The economic role of children: in countries where children work on family farms or support parents in old age, larger families bring an economic benefit, raising the birth rate.
4. State pension and social security provision: where the state provides pensions, parents rely less on children to support them in old age, which tends to lower the birth rate.
5. Religious and cultural attitudes: some religious or cultural beliefs encourage larger families, raising the birth rate in those communities.
6. Government population policy: some governments have at times restricted family size or offered incentives for larger families, directly affecting the birth rate.

These factors interact, so a single country can have a high or low birth rate for several reasons acting together rather than any one cause alone.

The infant mortality rate, the number of deaths of children under one year of age per 1000 live births, also affects the birth rate. Where many babies die young, parents may have more children to be sure that some survive to support them in old age, which raises the birth rate.

Why do death rates differ between countries?

Death rates tend to be lower in countries with higher standards of living, though again this is a general tendency rather than an absolute rule.

1. Quality of healthcare: better access to doctors, hospitals, vaccination and medicines reduces deaths from disease, lowering the death rate.
2. Diet and nutrition: a more varied and sufficient diet improves resistance to illness, lowering the death rate, while malnutrition raises it.
3. Clean water and sanitation: access to safe drinking water and proper sanitation reduces deaths from waterborne disease.
4. Age structure of the population: a country with a higher proportion of elderly people tends to have a higher death rate simply because older people are more likely to die in a given year.
5. War, conflict and natural disaster: these events raise the death rate sharply in the countries affected.

Death rates usually change gradually, but can fall rapidly during periods of rapid medical or public health improvement.

Death rates also differ because of life expectancy, the average number of years a person is expected to live. Countries with a high life expectancy usually have a low death rate, because most people survive to old age, while countries with a low life expectancy usually have a higher death rate.

Why does net migration differ between countries?

Migration decisions are usually explained using push factors and pull factors.

Definition: Push and pull factors. Push factors are conditions in a person's home country that encourage them to leave, such as unemployment, low wages, war or political persecution.

Pull factors are conditions in a destination country that attract people to move there, such as job opportunities, higher wages, political stability or family already living there.

Countries with strong economies, high wages and plentiful job opportunities tend to attract immigrants and so have positive net migration. Countries experiencing conflict, high unemployment or political instability tend to lose people through emigration, giving negative net migration.

Government immigration policy, for example the ease of obtaining a work visa, also strongly affects net migration, as does geographical proximity to wealthier countries.

Net migration also differs because of the age and skills of migrants. People of working age are more likely to move in search of work, so countries with strong demand for labour tend to attract younger migrants, while countries with few jobs tend to lose them.

What is the optimum population?

Definition: Optimum population. The size of population that, given the country's resources, technology and capital, produces the highest output per head.

Below the optimum population, there are not enough workers to make full use of the country's land, capital and natural resources, so output per head is lower than it could be: machinery may be left idle, farmland may be left unworked, and the economies of scale available from a larger workforce are not fully exploited.

Above the optimum population, there are too many workers relative to available resources and capital, so each additional worker adds less to total output than the workers before, and output per head falls again, even though total output may still be rising as the population grows.

The optimum population is not a fixed number for any country: it rises whenever a country gains more capital (such as new factories or machinery), better technology, or more usable resources, since these allow a larger workforce to be employed just as efficiently as a smaller one was before.

Conversely, the optimum population can fall if a country loses resources, for example through soil erosion or the depletion of a natural resource, meaning that a population that was once at its optimum can become either above or below it purely because its resources and capital have changed, without its actual number of people changing at all.

Output per head is total output divided by the number of people in the population. It is used as a measure of average living standards, so a population at its optimum is one where average output, and therefore average living standards, is at its highest.

What are the effects of an increase in population size?

An increase in population size can bring both benefits and costs to a country, and the overall effect depends on whether the increase is matched by a similar increase in resources, capital and jobs.

Benefits of an increasing population can include a larger workforce, which raises total output, a larger domestic market for firms to sell to, and a wider range of skills available in the labour force.

Costs can include greater pressure on housing, healthcare, education and other infrastructure, a higher risk of unemployment if jobs do not grow as fast as the labour force, and greater strain on natural resources and the environment.

If population growth pushes a country beyond its optimum population, output per head falls even while total output continues to rise, a situation often described as overpopulation.

A larger population can also bring more taxpayers, which raises government revenue and can help to fund public services. However, the same larger population needs more schools, hospitals and houses, so government spending rises at the same time.

What are the effects of a decrease in population size?

A falling population also brings a mixture of effects. If a country has been above its optimum population, a fall in numbers can raise output per head and ease pressure on housing, resources and infrastructure.

However, a persistently falling population, especially one caused by a falling birth rate, usually leads to underpopulation relative to the optimum: there are too few workers to make full use of the country's capital and resources, so output per head and total output can fall.

A shrinking working-age population also reduces tax revenue just as the proportion of elderly dependants is rising, making it harder for government to fund pensions, health care and other services, and firms may struggle to recruit enough workers, which can slow economic growth.

A falling population can also reduce the size of the domestic market, so firms may sell less and invest less. Schools and hospitals built for a larger population may be left partly unused, which is a waste of resources.

How do changes in age and gender structure affect a country?

Definition: Dependency ratio. The ratio of the number of dependants (people below and above working age) to the number of people of working age in a population.

A rise in the proportion of children or elderly people relative to the working-age population raises the dependency ratio, meaning each worker effectively supports more dependants.

An ageing population, where the proportion of elderly people is rising, increases government spending on pensions and healthcare, can create labour shortages in some industries, and may reduce the proportion of the population that is economically active.

A population with a high proportion of children also has a high dependency ratio, but for a different reason: the dependants are young rather than old. This raises spending on schools and childcare, and the children will later join the working-age population.

How does a change in gender distribution affect a country?

Changes in the gender balance of a population can also matter economically. For example, if large numbers of working-age men emigrate for work while women remain, the remaining population's age and gender structure changes, which can affect the local labour market, household incomes and the types of goods and services demanded.

A country whose migrants are mostly men of working age loses male workers in the industries that employed them, so firms in those industries may face labour shortages and have to raise wages or invest in machinery to replace them.

Households left behind may lose an earner, which can lower family income and change the pattern of demand, for example reducing spending on goods bought mainly by men and increasing spending on services used by women and children.

Where women remain in larger numbers, the share of women in paid work may rise, changing the types of jobs filled and the skills available to employers. A country that receives mostly male immigrants sees the opposite effect, with a larger male workforce and a different balance of demand.

Over time, an uneven gender balance can also affect the birth rate, because the number of couples able to have children is reduced when one sex is in short supply in the relevant age groups.

How is a population pyramid interpreted?

A population pyramid is a bar chart showing the number or percentage of males and females in each age group in a population, usually drawn with males on one side and females on the other, and age groups stacked from youngest at the bottom to oldest at the top.

An expanding pyramid has a wide base and narrows steadily towards the top, showing a high birth rate and relatively short life expectancy, typical of a country with a young, fast-growing population.

A stationary pyramid has roughly similar widths at each age group up to old age, where it narrows, showing a low and fairly stable birth rate and death rate.

A contracting pyramid has a narrow base, a bulge in the middle age groups and a long, narrower top, showing a falling birth rate and an ageing population.

From the shape of a pyramid, a student can read off the approximate birth rate (width of the base), the balance between males and females at each age, and the likely dependency ratio (the combined width of the youngest and oldest groups compared with the working-age middle groups).

The width of the base shows the number of children, which reflects the birth rate in recent years. A wide base means many children were born, so the birth rate is high. A narrow base means fewer children were born, so the birth rate is low or falling.

The height of the pyramid shows life expectancy. A tall pyramid with people in the oldest age groups means many people survive to old age, so life expectancy is high. A pyramid that narrows quickly towards the top means few people reach old age, so life expectancy is low.

The shape of the sides shows the death rate in each age group. If the sides slope inwards sharply, many people die young. If the sides are nearly vertical, most people survive from one age group to the next.

Why do population growth rates differ between countries?

Countries grow at very different rates because the three components of growth, the birth rate, the death rate and net migration, vary independently and can pull in opposite directions. A country with a high birth rate and a falling death rate grows quickly, while a country with a low birth rate and negative net migration can shrink.

In many low-income countries the birth rate is high and the death rate has fallen as basic healthcare, clean water and vaccination have spread. The gap between births and deaths is therefore wide, so natural increase is rapid and the population is young.

In many high-income countries both birth rates and death rates are low, so natural increase is small. Growth then depends mainly on net migration, and a country with more emigrants than immigrants can record a falling population even though births still exceed deaths.

Migration can also change a country's growth rate quickly, because migrants are usually of working age and may later have children in their new country, adding to the birth rate as well as to the population total.

Government policy matters too: a country that restricts family size or limits immigration will grow more slowly than one that encourages larger families or welcomes workers from abroad, even if their incomes and death rates are similar.

The overall growth rate therefore reflects which of the three components is dominant, and this balance changes as a country develops.

Going beyond the syllabus

These ideas extend the unit and are not needed for the questions on it.

What is the demographic transition model?

Many economists use a demographic transition model to describe how birth and death rates tend to change as a country develops over time. In the earliest stage, both birth rates and death rates are high, so population grows slowly.

Death rates usually fall first, as healthcare, clean water, sanitation and food supply improve, while birth rates remain high for longer, so population growth accelerates sharply in this middle stage.

Later, birth rates also begin to fall, as education (especially of women), access to family planning and rising living standards reduce the economic incentive to have large families, so population growth slows again.

In the final stage, both birth rates and death rates are low and population growth is slow or stable.

This model is a useful way of linking together the separate reasons for differing birth rates and death rates discussed above, since it shows how those reasons tend to change together as a country's income and development level rise, rather than changing in isolation.

It is important to remember, however, that this model describes a general pattern rather than a fixed law: actual countries do not always pass through its stages in the same order, at the same speed, or to the same degree, and some countries have reached low birth and death rates by a different route than the model describes.

Glossary

• Birth rate: the number of live births per 1000 of the population in a year.
• Death rate: the number of deaths per 1000 of the population in a year.
• Net migration: the difference between the number of immigrants and the number of emigrants in a period.
• Immigration: the movement of people into a country to live there.
• Emigration: the movement of people out of a country to live elsewhere.
• Push factor: a condition in a person's home country that encourages them to leave.
• Pull factor: a condition in a destination country that attracts people to move there.
• Optimum population: the population size that gives the highest output per head given a country's resources and capital.
• Overpopulation: a population larger than the optimum, where output per head is lower than it could be.
• Underpopulation: a population smaller than the optimum, where resources and capital are not fully used.
• Dependency ratio: the ratio of dependants (below and above working age) to people of working age.
• Ageing population: a population in which the proportion of elderly people is rising.
• Population pyramid: a bar chart showing the number of males and females in each age group of a population.
• Population growth rate: the percentage change in population size over a period, driven by births, deaths and net migration.

Common errors and misconceptions

• Misconception: a rising birth rate always means a growing population. Correct: population growth depends on births, deaths and net migration together; a rising birth rate can be offset by a rising death rate or negative net migration.
• Misconception: overpopulation simply means "too many people" in absolute terms. Correct: overpopulation is relative to a country's resources and capital; a small country can be overpopulated and a large country underpopulated.
• Misconception: immigration and net migration mean the same thing. Correct: immigration is only people entering; net migration is the balance of people entering minus people leaving.
• Misconception: an ageing population only affects elderly people. Correct: it affects government spending, the tax base, the labour supply and the dependency ratio for the whole economy.
• Misconception: a wide base on a population pyramid shows a large total population. Correct: it shows a high birth rate relative to the rest of the population, not necessarily a large total population.
• Misconception: all low-income countries have high birth rates and all high-income countries have low birth rates. Correct: this is a general tendency, not a rule; individual countries can differ because of education, policy, religion and other factors.
• Misconception: the optimum population is a fixed number for a country. Correct: it changes as capital, technology and resources change, so it can rise or fall over time.
• Misconception: a change in the gender balance of a population has no economic effect. Correct: it changes the labour supply, household incomes, the pattern of demand and possibly the birth rate.

Exam-style questions with model answers

Q1. Define 'net migration'. [2 marks]

1. Net migration is the difference between the number of people entering a country and the number leaving it in a period.
2. If more people enter than leave, net migration is positive; if more leave than enter, it is negative.

Q2. A country has a birth rate of 14 per 1000, a death rate of 9 per 1000 and net migration of −1 per 1000. Calculate the population growth rate. Show your working. [2 marks]

1. Population growth rate = birth rate − death rate + net migration rate = 14 − 9 + (−1).
2. 14 − 9 − 1 = 4 per 1000, so the population growth rate is 4 per 1000 (0.4%).

Q3. Identify two factors that could cause a country's birth rate to fall. [2 marks]

1. Wider access to family planning and contraception, which allows couples to plan family size.
2. Higher levels of education for women, which is associated with women entering paid work and having fewer children later in life.

Q4. Explain one reason why death rates tend to be lower in high-income countries than in low-income countries. [2 marks]

1. High-income countries usually have better access to healthcare, including doctors, hospitals and vaccination programmes.
2. This better healthcare reduces deaths from disease and treatable illness, lowering the death rate.

Q5. Explain two reasons why the population growth rate of one country may be much higher than that of another. [4 marks]

1. The first country may have a much higher birth rate, for example because contraception and female education are less widespread, so more children are born per 1000 of the population.
2. Its death rate may also have fallen as basic healthcare, clean water and vaccination have spread, so the gap between births and deaths is wide and natural increase is rapid.
3. The second country may have a low birth rate and a low death rate, so its natural increase is small.
4. The second country may also have negative net migration, with more people leaving than arriving, which reduces its growth rate further.

Q6. Analyse how a change in the gender distribution of a population can affect a country's economy. [4 marks]

1. If many working-age men emigrate while women remain, firms in the industries that employed those men may face labour shortages and have to raise wages or invest in machinery.
2. Households left behind may lose an earner, lowering family income and changing the pattern of demand for goods and services.
3. Where women remain in larger numbers, the share of women in paid work may rise, changing the skills available to employers.
4. An uneven gender balance can also lower the birth rate, because fewer couples are able to have children when one sex is in short supply in the relevant age groups.

Q7. A country's population pyramid has a wide base that narrows quickly towards the top. Analyse what this shape suggests about the country's birth rate and dependency ratio. [4 marks]

1. A wide base represents a large number of young children relative to other age groups, which indicates a high birth rate.
2. The pyramid narrowing quickly towards the top shows relatively few people reaching old age, which can indicate a lower life expectancy.
3. Because there are many children compared with working-age adults, the dependency ratio is likely to be high.
4. A high dependency ratio means each working-age person effectively supports more dependants, which can limit output per head and strain education and family resources.

Q8. Discuss whether a rapid increase in population size is likely to raise or lower a country's standard of living. [8 marks]

1. A rapid increase in population raises the size of the workforce, which can increase total output if enough jobs are created.
2. A larger population also creates a larger domestic market, which can encourage firms to invest and expand.
3. However, if the population grows faster than jobs, unemployment may rise, reducing household incomes for some families.
4. Greater demand for housing can raise housing costs if supply does not keep pace.
5. Greater pressure on healthcare and education can reduce the quality of these services per person if spending does not rise proportionately.
6. If the increase pushes population above the optimum level, output per head can fall even while total output rises, lowering average living standards.
7. Whether living standards rise therefore depends on whether the increase is matched by investment in capital, jobs and infrastructure.
8. A country that invests ahead of the increase, for example in schools, hospitals and factories, is more likely to gain from a larger workforce and market than one that does not.

Key takeaways

• Population growth depends on the birth rate, the death rate and net migration acting together.
• Birth and death rates are measured per 1000 of the population so that countries of different sizes can be compared.
• Net migration is positive when immigration exceeds emigration and negative when emigration exceeds immigration.
• Birth rates tend to be higher where healthcare, education and pensions are limited, though this is a general tendency, not a rule.
• Death rates tend to be lower where healthcare, nutrition and sanitation are better.
• Migration is usually explained by push factors in the home country and pull factors in the destination country.
• Growth rates differ between countries because the three components vary independently and can pull in opposite directions.
• The optimum population gives the highest output per head for a given level of resources and capital, and changes over time.
• Population above the optimum is overpopulation; population below it is underpopulation.
• An ageing population raises the dependency ratio and increases pressure on pensions and healthcare spending.

Test yourself

What three factors determine whether a country's population is growing or shrinking?

The birth rate, the death rate and net migration together determine whether population is growing or shrinking.

Why are birth and death rates usually expressed per 1000 of the population rather than as totals?

Expressing them per 1000 allows fair comparison between countries of different population sizes.

Give one push factor and one pull factor that could explain migration between two countries.

A push factor could be high unemployment at home; a pull factor could be higher wages or job opportunities abroad.

Why can a country with a low birth rate still have a rising population?

Its population can rise if net migration is strongly positive, with more immigrants arriving than emigrants leaving.

What happens to output per head if population rises above the optimum population?

Output per head falls, even though total output may still be rising, because resources and capital are spread over too many workers.

What does a rising dependency ratio mean for workers in a country?

Each worker of working age must, on average, support more dependants, such as children and elderly people.

What shape would you expect a population pyramid to have for a country with a high birth rate and short life expectancy?

A wide base that narrows quickly towards the top, known as an expanding pyramid.

How can a change in the gender balance of a population affect the birth rate?

If one sex is in short supply in the relevant age groups, fewer couples are able to have children, so the birth rate may fall.