What this lesson teaches
I can define birth rate, death rate and net migration, and explain why they differ between countries.
Syllabus K343, 5.3.1. Factors that affect population growth: definitions of: birth rate, death rate, net migration, immigration and emigration; how birth rates, death rates and net migration can vary between countries; reasons why birth rates, death rates and net migration rates can vary between countries
Make a guess
A country's birth rate falls every year. Must its population be shrinking?
- Yes, because the death rate must be higher.
- Yes. Fewer babies always means fewer people.
- No, not while births still exceed deaths.
Show the answer
No, not while births still exceed deaths.
A falling birth rate slows growth. The population shrinks only when deaths plus emigration exceed births plus immigration.
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%.
Try it step by step
Problem 1
In a year, a country has 50,000 births, 30,000 deaths, 12,000 immigrants and 8,000 emigrants.
Show the working
- Natural increase: 50,000 - 30,000 = 20,000
- Net migration: 12,000 - 8,000 = 4,000
- Total change in population: 20,000 + 4,000 = 24,000 more people
Problem 2
In a year, a country has 32,000 births, 26,000 deaths, 25,000 immigrants and 9,000 emigrants.
Show the working
- Natural increase: 32,000 - 26,000 = 6,000
- Net migration: 25,000 - 9,000 = 16,000
- Total change in population: 6,000 + 16,000 = 22,000 more people
Problem 3
In a year, a country has 20,000 births, 28,000 deaths, 15,000 immigrants and 4,000 emigrants.
Show the working
- Natural increase: 20,000 - 28,000 = -8,000 (a natural decrease)
- Net migration: 15,000 - 4,000 = 11,000
- Total change in population: -8,000 + 11,000 = 3,000 more people
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
Show the answer
Negative
Right. Net migration = immigration - emigration, which is below zero here.
Check your understanding
In a year a country has 40,000 births, 25,000 deaths, 30,000 immigrants and 10,000 emigrants. By how much does its population change?
- It rises by 15,000
- It rises by 20,000
- It rises by 35,000
- It rises by 105,000
Show the answer
It rises by 35,000
Right. Natural increase is 15,000 and net migration is 20,000, so the population rises by 35,000.