Population inputs at Higher Level: The same two inputs as SL, met through different real cases: Canada, which grew faster than any rich country in 2023 through immigration, and Italy, whose births hit a 160-year low.
Practise this as you read
- Calculate a crude birth rate and an immigration rate, formula first.
- Judge which input drives a country's growth from its numbers.
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What adds people to a population: Think of a population as a tank of people. Two taps fill it: babies being born, and people moving in, called immigration.
The points to remember
- A human population is a system: people are added and lost every year.
- The inputs add people: births and immigration.
- Immigration = people moving into a place to live there.
- More births or more immigrants make the population grow, unless outputs rise as much.
- Births add babies; immigrants are often young adults, who may then have children there.
Remember it as: Born here or moved here: both are inputs.
Real example: Canada grew by 1,271,872 people in 2023 (3.2%), its fastest growth since 1957. 97.6% of that growth came from people moving in, not from births.
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Counting births is not enough to compare places: a big country has more births just because it has more people. So births are turned into a rate, the crude birth rate.
Crude birth rate
- Crude birth rate (CBR) = the number of live births per 1000 people in a population per year.
- Formula: CBR = births ÷ total population × 1000.
- Always give the unit: per 1000 (per thousand) people per year.
- It is crude: it counts the whole population, men, children and old people too.
- So it shows how fast births add people, not how many children each woman has.
Worked example: Italy, 2024: about 370,000 babies were born in a population of about 59 million.
CBR = births ÷ population × 1000 = 370,000 ÷ 59,000,000 × 1000 = 6.3 per 1000 per year.
Real example: Italy's 370,000 births in 2024 were the fewest since 1861. India, with far more young adults, has more births every year than any other country.
Do not forget the unit: A rate with no unit is just a number. Write 'per 1000' (or per thousand) every time.
People moving in are measured the same way: the immigration rate. An immigrant}} is counted in the place they arrive.
Immigration rate
- Immigration rate = the number of immigrants per 1000 people in the population per year.
- Formula: immigration rate = immigrants ÷ total population × 1000.
- Immigrants are counted where they arrive: they are an input there.
- People move in for jobs, family, study, or to escape war and disasters.
- A high immigration rate can make a population grow even when few babies are born.
Worked example: Canada, 2023: 471,771 people arrived as new permanent residents; the population was about 40.1 million.
Immigration rate = 471,771 ÷ 40,100,000 × 1000 = about 11.8 per 1000 per year.
Births
- New people, born in the place
- Measured by the crude birth rate
- Adds babies, who need schools first
Immigration
- People who move in
- Measured by the immigration rate
- Often adds young adults, who can work at once
Real example: Canada's permanent immigrants alone (about 11.8 per 1000) outnumbered its births in 2023.
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The rates are used at every scale, from a small town to the whole planet. Because each is 'per 1000 people', a town of 48,000 can be compared fairly with a country of 84 million.
Using the rates
- The same rates work for a town, a country, a region or the whole world.
- Per 1000 lets you compare places of very different size fairly.
- Totals mislead: a big country has more births just because it has more people.
- Both rates are averages (mean values) for one year.
- The world has no immigration: births are its only input.
| Scale | Inputs | Example |
|---|---|---|
| A town | Births + people moving in from other towns or countries | A new factory brings workers |
| A country | Births + immigrants from abroad | Canada 2023: students and workers |
| The world | Births only: nobody moves in from outside | 8.2 billion people in 2024 |
No immigration for the world: For the global population, migration does not count: people only move from one country to another. Births are the world's only input.
Real example: India grows mainly through births; Canada grows mainly through immigration.
How this comes up: Calculate a crude birth rate or an immigration rate from a fact file [1]; read births and immigrants from a chart [1-2]; outline why rates are given per 1000 [2]; compare two rates [4].
In 2023 Canada's population grew by 1,271,872 people. About 351,000 babies were born, and 97.6% of the growth came from international migration.
Outline the contribution of the two inputs to Canada's population growth in 2023.
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