2281 · 5.3
Population
A population grows when births and immigration outnumber deaths and emigration. As countries develop, births fall and people live longer, so the population ages — and fewer workers must support more pensioners.
Need to know
What you need to know
- Birth rate and death rate are measured per 1 000 people per year.
- Natural increase = birth rate − death rate; add net migration for total growth.
- Growth rate of 1.4% a year doubles a population in about 50 years (rule of 70).
- Fertility rate of about 2.1 births per woman is the replacement level.
Explanation
Population
- Growth = birth rate − death rate + net migration, measured per 1 000 people.
- Birth rates fall as countries develop; death rates fall with health and sanitation.
- The dependency ratio compares the young and old with the working-age population.
- An ageing population raises pension and health costs and shrinks the workforce.