Why population data matters
Governments, businesses and communities need to know how many people live where, and who they are, to plan schools, hospitals, transit, housing and services. Geographers study population data to find spatial patterns: the ways people and features are arranged across the land.
Where data comes from: the census
A census is an official count of the population.
- Canada: Statistics Canada runs a census every five years (2016, 2021, 2026…).
- United States: the U.S. Census Bureau runs a census every ten years (2010, 2020, 2030…). The results decide how many seats each state gets in the House of Representatives.
Censuses collect information on age, sex, household size, language, income, housing, Indigenous identity, immigration and more. Personal answers are kept confidential by law.
Population density
Population density = number of people ÷ land area.
| Place | Approximate density (people per km²) |
|---|---|
| Canada (whole country) | about 4–5 |
| United States | about 37 |
| Toronto (city) | over 4,000 |
| Nunavut | far below 1 |
| Bangladesh | over 1,000 |
Density averages can hide big differences. Canada’s average is low, but its cities can be very dense.
Population distribution
Population distribution describes where people live.
- Concentrated: many people in a small area, such as cities and river valleys.
- Sparse: few people spread over a large area, such as the Arctic or deserts.
In Canada, about 90% of people live within roughly 160 km of the U.S. border. Most live in the Windsor–Québec City corridor, the Lower Mainland of British Columbia, and the Calgary–Edmonton corridor.
Common spatial patterns
| Pattern | Looks like | Example |
|---|---|---|
| Clustered | points grouped together | cities, shopping districts |
| Linear | points along a line | towns along a highway, river or railway |
| Dispersed | points spread out | farms on the Prairies |
| Random | no clear pattern | some natural features |
Population change
A population changes through births, deaths and migration.
Population growth = (births − deaths) + (immigrants − emigrants)
- Birth rate: births per 1,000 people per year
- Death rate: deaths per 1,000 people per year
- Natural increase: birth rate minus death rate
- Net migration: people moving in minus people moving out
In Canada, immigration accounts for most population growth, because the birth rate is low and the population is aging.
Population pyramids
A population pyramid shows how many males and females are in each age group.
| Shape | What it shows | Example |
|---|---|---|
| Wide base, narrow top (triangle) | high birth rate, young population, growing quickly | many countries in sub-Saharan Africa |
| Straight sides (column) | slow growth, steady birth rate | United States |
| Narrow base (inverted or "top-heavy") | low birth rate, older population | Japan, Italy; Canada is moving this way |
The large "baby boom" generation (born roughly 1946–1965) creates a bulge in Canadian and American pyramids.
Reading population maps
- Choropleth maps shade areas by value, such as darker colours for higher density.
- Dot maps use dots, each representing a certain number of people.
- Proportional symbol maps use larger circles for larger populations.
Always check the legend, the scale and the date of the data.
Using data to make decisions
| Data shows… | Possible decision |
|---|---|
| many young families moving to a suburb | build new schools and parks |
| aging population in a town | more health care and senior housing |
| fast-growing city | expand transit and housing |
| shrinking rural population | maintain services, attract new residents |
Thinking critically about data
- Is the data up to date?
- Who collected it, and how?
- Are some groups undercounted, such as people experiencing homelessness or remote communities?
- Does an average hide important differences?
Try it yourself
- Calculate the population density of your town using its population and land area.
- Find Statistics Canada or Census Bureau data for your community. What patterns do you notice?
- Draw population pyramids for a young country and an aging country, and explain the differences.
- Map the locations of schools in your area. Is the pattern clustered, linear or dispersed?
Quick recap
- Censuses collect population data for planning.
- Population density is people per unit of area.
- Population distribution shows where people live; Canadians are concentrated in the south.
- Populations change through births, deaths and migration.
- Population pyramids show age structure, and maps reveal spatial patterns.