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Using age-sex structure diagrams to predict the future needs and challenges of a society.
Imagine you are a city planner in the year 2050. How would you know today whether you should build more elementary schools or more retirement homes? The answer is hidden in the shape of a pyramid.
A population pyramid (or age-sex structure diagram) is a specialized bar graph that shows the distribution of various age groups in a population. The graph is split down the middle: males are displayed on the left, and females are on the right. The vertical axis (y-axis) shows age cohorts, usually in 5-year increments (e.g., 0-4, 5-9). The horizontal axis (x-axis) measures the population size, often as a percentage of the total population. By looking at the 'width' of each bar, we can see which age groups are the largest.
To find the percentage of young females (ages 0-4) in a country: 1. Locate the bottom-most bar on the graph. 2. Look at the right-hand side (the female side). 3. Read the value on the x-axis. If the bar ends at the number 5, then of the total population consists of girls under age 5.
Quick Check
If a population pyramid has a very wide base, what does that tell you about the number of children in that society?
Answer
A wide base indicates a high birth rate and a large population of young children.
The overall shape of the pyramid tells a story about a country's development. An Expansive pyramid looks like a true triangle with a wide base; this indicates rapid growth and high birth rates. A Stationary pyramid looks more like a rectangle or a 'beehive,' showing stable growth where birth rates roughly equal death rates. Finally, a Constrictive pyramid is narrower at the bottom than in the middle; this indicates an aging population with low birth rates, common in many highly developed nations.
Quick Check
Which pyramid shape would likely have the highest 'Youth Dependency' (more children than workers)?
Answer
The Expansive (triangular) pyramid.
Population pyramids are 'crystal balls' for governments. If a pyramid has a bulge in the middle (the working-age group), that country may experience an economic boom. However, as that bulge moves upward over time, the country must prepare for a 'silver tsunami'—a massive increase in elderly citizens. Conversely, a country with a very narrow base today will face a labor shortage in 20 years, as there won't be enough young people to fill jobs left by retirees.
Imagine Country A has a wide base ( of population is 0-4) and Country B has a narrow base ( is 0-4) but a wide top ( is 70+). 1. Country A must prioritize budgeting for new schools and pediatricians. 2. Country B must prioritize geriatric healthcare and pension fund stability. 3. If Country B's birth rate stays low, they may need to encourage immigration to maintain their workforce.
What does a 'beehive' or rectangular-shaped pyramid indicate?
If a pyramid is 'top-heavy' (wider at the ages of 60+ than at 0-14), what is the most likely future challenge?
In a population pyramid, males and females are always represented on the same side of the vertical axis.
Review Tomorrow
In 24 hours, try to sketch the three main types of population pyramids (Expansive, Stationary, Constrictive) from memory and list one challenge for each.
Practice Activity
Find the 2023 population pyramid for your own country online. Is the base wider or narrower than the middle section? What does this suggest about your country's future?