Population and development
- Population change = natural change + net migration.
- Natural change = birth rate − death rate.
- The size and structure of the population affect output per head and living standards.
Key Idea
- Birth rate, death rate, infant mortality and net migration together drive population change.
- The optimum population maximises output per head, and urbanisation shifts people from rural to urban areas.
Measuring population change
Definition
Birth rate: the number of live births per thousand of the population each year.
Death rate: the number of deaths per thousand of the population each year.
Infant mortality rate: deaths of children under one per thousand live births.
Net migration: immigration − emigration over a period.
- The birth rate falls with higher incomes, more female education and employment, and better access to contraception, as families choose fewer children.
- The death rate falls with better healthcare, nutrition and sanitation, though an ageing population can later push it back up.
- Infant mortality falls with better maternal healthcare, immunisation, clean water and nutrition, making it a sensitive marker of development.
- Net migration responds to wage differences, job opportunities, conflict and immigration policy, changing both the size and the skill mix of the workforce.
Example
- Suppose a country of 20 million has a birth rate of 30 per 1,000, a death rate of 10 per 1,000 and net migration of +50,000 in a year.
- Work through it step by step.
- The population rises by 450,000 (about 2.25%), with the natural increase of 400,000 dwarfing net migration of 50,000.
Note
- In many developing economies the death rate falls before the birth rate, so the population grows rapidly for a period.
- Migration also reshapes the age and skill structure, not just the total.
Optimum population
Definition
Optimum population: the population size that maximises real output per head, given the country's resources, capital and technology.
- Below the optimum a country is underpopulated, so land and capital are not fully used and output per head is below its potential.
- Above the optimum a country is overpopulated, so resources are stretched and output per head falls.
- The optimum is not fixed: new technology or resource discoveries raise the population a country can productively support.
Example
- A resource-rich, sparsely populated economy may be underpopulated, while a crowded low-income one is overpopulated.
- The same population could be optimal for one country and excessive for another, so it depends on resources and technology.
Level of urbanisation
Definition
Level of urbanisation: the share of the population living in towns and cities.
- Urbanisation rises with development as workers move from low-productivity farming to higher-productivity industry and services.
- This shift can raise output per head and widen access to education and healthcare.
- But rapid rural-urban migration may bring congestion, informal settlements and strained public services, offsetting some of the gains.
Exam technique
- Define each rate precisely, including its per-thousand basis.
- Link a cause of population change to its effect on output per head.
- Judge whether a country is under, over or optimally populated using its resources and technology.
Common Mistake
- Do not treat a larger population as automatically good or bad, since it depends on the optimum.
- Do not confuse the birth rate with the fertility rate, or the death rate with infant mortality.
Self review
- How is natural population change calculated?
- Give one cause each of a falling birth rate and a falling death rate.
- Define the optimum population.
- What is meant by the level of urbanisation?
- Distinguish overpopulation from underpopulation.
