Population

Birth rate and death rate

The birth rate is the number of live births per 1,000 people per year.

The death rate is the number of deaths per 1,000 people per year.

Natural population change

Natural population change = births − deaths.

A positive natural change means the population is growing from within; a negative natural change means more people are dying than being born.

Net migration

Immigration is the movement of people into a country to live there. Emigration is the movement of people out of a country to live elsewhere.

Net migration = immigration − emigration over a period. A positive figure is a net inflow; a negative figure is a net outflow.

Net migration adds to or subtracts from the population independently of natural change. Some countries grow despite low natural change because of strong net inward migration (e.g. Canada, Australia in recent years). Others shrink despite positive natural change because emigration outpaces it.

Total population change

Total population change = (births − deaths) + net migration.

Why these rates vary between countries

All three rates differ sharply between countries, and questions often ask you to explain why.

Birth rates are highest where children are cheap to raise and economically useful, and lowest where they are expensive and where women have other opportunities. The main influences are:

• Female education and workforce participation. Women who stay in education longer and hold paid jobs tend to have fewer children, and to have them later.
• Access to contraception and family planning, and how far it is socially and religiously accepted.
• Infant mortality. Where many children die young, families choose to have more, so a falling infant mortality rate eventually pulls the birth rate down.
• The cost of raising children. Schooling, housing and childcare are expensive in richer, urbanised economies. In poorer rural economies children add to family labour and support parents in old age, especially where there is no state pension.
• Culture, religion and social norms about family size and the age of marriage.
• Government policy, from family-planning programmes that lower the birth rate to child benefits and paid parental leave intended to raise it (section 6).

Death rates depend mainly on health, living conditions and the age of the population:

• Quality and availability of healthcare: doctors, hospitals, vaccination programmes, medicines.
• Nutrition, and access to clean water and sanitation.
• Income and living standards, which pay for better housing, diet and safety at work.
• Age structure: a country with a large elderly share has a higher death rate even if it is healthier, because more of its people are near the end of life.
• Conflict, natural disasters and pollution, which raise deaths well above the underlying trend.

Net migration depends on the balance of push and pull factors, and on what governments allow:

• Wage and job differences. People move towards higher wages and better employment prospects.
• Political stability. Conflict, persecution and insecurity push people out; safety pulls them in.
• Immigration rules and visa systems, including points-based schemes for skilled workers and refugee programmes.
• Family, community and language ties, which make some destinations far easier to settle in than others.
• Environmental pressure, such as drought, flooding or crop failure driving people away from affected regions.

The typical pattern is that low-income countries have high birth rates with death rates that are falling quickly, so their populations grow fast and are young. High-income countries have low birth and death rates, so their populations grow slowly, or shrink, and are ageing. Migration usually runs from lower-wage to higher-wage countries, which reinforces both patterns: it adds working-age people to the richer country and removes them from the poorer one.

Dependency ratio

The dependency ratio is the ratio of the non-working-age population (children plus elderly) to the working-age population, usually expressed as a percentage.

$\text{Dependency ratio (\%)} = \dfrac{\text{Non-working-age population}}{\text{Working-age population}} \times 100$

The working-age range is usually defined as 15–64. Dependants are everyone outside that range: under-15s and over-65s.