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What the shape indicates
The shape of a population pyramid can indicate:
Growing population: A pyramid shape indicates a growing population
Shrinking population: A cup shape indicates a shrinking population
High birth rate: A wide base indicates a high birth rate
Low birth rate: A narrow base indicates a low birth rate
High proportion of people living longer: A broad top indicates a high proportion of people living longer
Low death rate: Straight or near vertical sides indicate a low death rate
A population pyramid, also known as an age-sex pyramid, can show the distribution of a population by age and sex as a percentage of the total population:
What it shows
A population pyramid is a graph that shows the percentage of a population that is in a certain age range and gender. It's made up of two back-to-back horizontal histograms, one for males and one for females.
How to interpret it
You can use a population pyramid to:
Compare the male and female populations of an area
See the number of dependents (children and sometimes elderly people)
Predict what will happen in the future and what services may be needed
Understand the reproductive capabilities and likelihood of a species' continuation
Task One - Draw a line from the description of the population pyramids (below) to the correct pyramid it represents.
1. A rather square-shaped population pyramid refers to a population with slow population growth: There are fewer births and fewer younger people, but more older people due to the lower mortality rate and higher life expectancy.
2. This example of a population pyramid is based on population decline: In countries with a very low birth and mortality rate, the population declines instead of grows. Due to a high life expectancy and the low birth rate, the population undergoes an ageing process: Fewer children are born, but the majority of them live until a high age.
3. Population structures with a pyramid shape indicate a young population and relatively strong population growth: A large number of new-borns and youth form the basis of the pyramid so that it is wider at the bottom and becomes increasingly smaller and narrower at the top among the older age groups. This type of population pyramid typically has a considerable mortality rate, which creates a very sharply contoured figure.
To calculate the number of people from a percentage in a population pyramid, you can use the equation for each age and gender cohort:
Equation =C5/B3
Explanation: C5 is the value for a specific age and gender cohort, and B3 is the total population of both sexes
You can repeat this process for each age cohort, making sure to keep the denominator (B3) the same.
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