Population Pyramids and Growth
Population Pyramids
• This is a graphic way of depicting population
data
• The graph always the demographers to break
down each sub-group into 5 years, those subgroups are called: Cohorts.
• The graph can help us obtain a very clear
picture of the population’s age-sex
composition
What to look at??
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Width of Base
Symmetry
Shape
Bumps
Width of Base
What does a base of this tell us about this country? What
Geographic terms can be used?
Symmetry
Shape
Concave
Convex
Bumps
3 main types
• Expansive: triangular in shape
• Constrictive: smaller base, can be shaped like
hour glass
• Stationary: rectangular shaped
Expansive
These are usually found in developing or third world countries. The large base,
Birth rate, is extremely high. Lower life expectancy and life is going to be tough
For these countries. Population is increasing, but the lower life expectancy keeps
The population from exploding.
Constrictive
These pyramids are usually done in developed nations. However, the larger
The base the more population growth will happen. Indicates low birth rates, but
The life expectancy is also high. Somewhat equal numbers throughout cohorts.
Stationary
Age cohorts are close to the same throughout pyramid. This shows
Even growth within the countries. These pyramids show up in developed
Nations.