Grade by Grade
B. Global Inequalities: Economic Development and Quality of Life · Global Inequalities: Economic Development and Quality of Life

Population Pyramids: Reading the Shape of a Population

B3.4 B2.4About 50 minutes
Learning goals
  • I can read a population pyramid and describe its shape.
  • I can construct a population pyramid on paper and with a graphing program.
  • I can connect pyramid shapes to birth rates, death rates, life expectancy and development.
  • I can use a pyramid to predict future needs, such as schools or senior care.

Words to know

population pyramid
A pair of horizontal bar graphs, back to back, that shows the percentage of males and females in each age group of a population.
age group (cohort)
A group of people born in the same span of years, usually shown in 5-year groups such as 10 to 14.
expanding pyramid
A pyramid with a wide base and narrow top: many children, fewer older people. Usually high birth and death rates.
stable pyramid
A pyramid with straight, column-like sides: similar numbers in most age groups, with fewer at the oldest ages.
contracting pyramid
A pyramid with a narrower base than its middle: low birth rate and an ageing population.
dependency ratio
The number of people aged 0 to 14 and 65+ for every 100 people aged 15 to 64.
baby boom
A period with many more births than usual. In Canada, roughly 1946 to 1965.

Hook: a population's portrait

If you lined up everyone in your school by age, what would the line look like? A population pyramid draws that kind of picture for a whole country. Its shape tells a story about births, deaths, health care and even history.

How to read a population pyramid

  • The vertical axis shows age groups, youngest at the bottom, oldest at the top.
  • The horizontal axis shows the percentage of the whole population (sometimes the number of people).
  • Males are on one side and females on the other.
  • Each bar is one age group. Wider bar = more people in that group.
0–910–1920–2930–3940–4950–5960–6970–7980+AgeMalesFemales← % of population →Oldest at the topYoungest at the bottomLonger bar =more peoplein that group
How to read a pyramid (made-up numbers, for labels only). Males are on the left, females on the right, and each pair of bars is one age group.
ExpandingStableContracting
Three common shapes. In each pyramid the youngest age group is at the bottom and the oldest at the top; the left side shows males and the right side shows females.
ShapeWhat it suggestsReal-world pattern
Expanding (wide base)High birth rate, more deaths at younger ages, young population, fast growthIn countries such as Niger and Mali, nearly half the people are under 15 (UN World Population Prospects)
Stable (column)Birth and death rates both lower and steady; slow growthSome countries pass through this stage as birth rates fall
Contracting (narrow base)Low birth rate, long life expectancy, ageing population; may shrinkIn Japan, almost 3 in 10 people are 65 or older
Pyramid shapes and what they suggest. Many countries' shapes change as they develop.

Canada's pyramid

Canada's pyramid has a narrow base and a wide middle and upper part. It shows a big bulge for the baby boom generation, born roughly 1946 to 1965, who are now seniors. In 2016, for the first time, the census counted more people aged 65 and older than children under 15 (Statistics Canada). In Canada, as in most countries, women live longer on average than men (by about 4 years in Canada), so the top of the pyramid is wider on the female side.

Canada's population still grows, mainly because of immigration. Many newcomers are young adults, which widens the working-age bars.

Just for fun

Population "pyramids" are not always pyramid-shaped. A contracting one, like Japan's, looks more like a vase or a lampshade, and a stable one looks like a tall box. Geographers kept the name anyway, because "population lampshade" doesn't sound as smart.

Why it matters: planning for the future

A pyramid helps governments plan:

  • Wide base: more schools, teachers, vaccines and, later, jobs.
  • Wide top: more health care, long-term care homes and pensions, and fewer workers paying taxes for each retired person.

The dependency ratio compares people who are usually not working (0 to 14, 65+) with working-age people (15 to 64).

Worked example

Let's construct one bar and a dependency ratio

A fictional town of 10 000 people has 1 500 boys aged 0 to 14, 1 400 girls aged 0 to 14, 6 100 people aged 15 to 64 and 1 000 people aged 65+. What percentage is the boys' 0 to 14 bar? What is the dependency ratio?

  1. Percent for a bar = number in group ÷ total population × 100.
  2. Boys 0 to 14: 1 500 ÷ 10 000 × 100 = 15%. Draw a bar 15 units long on the male side.
  3. Dependents: 1 500 + 1 400 + 1 000 = 3 900. Working age: 6 100.
  4. Dependency ratio: 3 900 ÷ 6 100 × 100 ≈ 64.

The boys' 0 to 14 bar is 15%, and there are about 64 dependents for every 100 working-age people.

Worked example

Let's make a pyramid with a graphing program

How can you build a pyramid in a spreadsheet?

  1. Make three columns: Age group, Males (%), Females (%).
  2. Type the male values as negative numbers (for example −4.2) so their bars go left.
  3. Insert a bar chart (horizontal bars), then set the bars to overlap fully with no gap.
  4. Format the axis labels to hide the minus signs, and add a title, axis labels and the source. Free online tools from the UN and other sites also draw pyramids for any country.

Negative male values make the bars point left, creating the pyramid shape.

Hands-on activity

Family pyramid

You need: paper, a pencil, a ruler and a list of everyone in your extended family (or your street, with permission, using ages only, no names).

  1. Sort people into age groups: 0 to 9, 10 to 19, 20 to 29 and so on.
  2. Count males and females in each group (or draw a single-sided bar graph if you prefer not to sort by sex).
  3. Draw horizontal bars back to back, youngest at the bottom.
  4. Describe your shape: expanding, stable or contracting? What would your family or street need in 10 years?

Look for: bars in age order, a labelled axis, and a sensible prediction (for example, "more teenagers soon, so more need for high school spaces"). A small group will not look like a country, and that is fine.

Your turn

1

What does the base of a population pyramid show?

2

A pyramid has a very wide base and a narrow top. Describe the population.

3

Why is the top of Canada's pyramid wider on the female side?

4

What was the baby boom in Canada?

5

A town has 2 000 people; 260 are girls aged 5 to 9. What percent is that bar?

6

Name two services a country with a contracting pyramid will need more of.

7

Why does Canada's population still grow even though its birth rate is low?

More practice: warm-up

1

Where are the oldest people shown on a pyramid?

2

Name the three main pyramid shapes.

3

Which shape fits a country where nearly half the people are under 15?

4

What does each bar show?

5

Which shape fits Japan?

More practice: on your own

1

Calculate the dependency ratio: 0 to 14: 4 000; 15 to 64: 5 000; 65+: 1 000.

2

A pyramid has a sudden narrow band for people aged 75 to 79 compared with the groups above and below. Suggest two causes.

3

Explain how falling infant mortality changes a pyramid over time.

4

A country's pyramid has a much wider 20 to 34 group for males than females. Suggest a reason.

5

Why is the dependency ratio high in both expanding and contracting populations?

Challenge

1

Predict what Mali's pyramid might look like in 40 years if the fertility rate falls and health care improves. Explain.

2

A country has a large working-age bulge and a narrowing base. Some economists call this a chance for growth. Why? What is needed to take advantage of it?

3

Using the dependency ratio, explain one challenge Canada will face as baby boomers age, and one possible solution.

Check your understanding

Quiz

1.

On a population pyramid, the youngest age group is shown…

2.

A wide base and narrow top usually means…

3.

Which country has a contracting pyramid with almost 3 in 10 people aged 65 or older?

4.

A town has 5 000 people; 400 are boys aged 0 to 4. What percent is that bar?

5.

Dependency ratio compares…

6.

In a spreadsheet pyramid, male values are often entered as negative numbers so that…

For parents and teachers

What this lesson is about: reading and constructing population pyramids (B3.4) and connecting shapes to development.

How to help at home:

  • Look at Canada's pyramid together on Statistics Canada's population pyramid tool, and compare it with another country's on a UN or similar site.
  • In the family activity, use ages only; your child can skip the male/female split if you prefer.

Common difficulties:

  • Thinking the pyramid shows change over time (it is a snapshot of one year).
  • Forgetting that bars show percent of the whole population, not percent of one sex.
  • Explaining every narrow band with deaths, when lower births or migration may be the cause.