Population changes through births, deaths and net migration.
The birth rate is the number of live births per 1,000 people in a year. The death rate is the number of deaths per 1,000 people in a year. The difference between them is the rate of natural increase.
Immigration is people moving into a country to live. Emigration is people leaving to live elsewhere. Net migration = immigration - emigration. Positive net migration adds to the population; negative net migration reduces it.
A population grows when births plus immigration are greater than deaths plus emigration.
Countries differ a great deal. Many low-income countries have high birth rates and young populations. Many high-income countries, including Singapore, have low birth rates and ageing populations.
- Birth rate
- Live births per 1,000 people per year.
- Death rate
- Deaths per 1,000 people per year.
- Net migration
- Immigration - emigration.
Worked example: Working out a population change
Suppose a country of 10 million has a birth rate of 12 per 1,000 and a death rate of 8 per 1,000. Net migration is +20,000 in the year.
- Births = 12 x 10,000 = 120,000. Deaths = 8 x 10,000 = 80,000.
- Natural increase = 120,000 - 80,000 = 40,000.
- Add net migration: 40,000 + 20,000 = 60,000.
- The population grows by 60,000, or 0.6%.
Watch out for this
A falling birth rate means the population must be shrinking.
The population still grows if births exceed deaths, or if net migration is positive. A falling birth rate slows growth, but does not necessarily reverse it.
Check your understanding
A country has more emigrants than immigrants. What is its net migration?
- Negative
- Positive
- Zero