There are generally three types of population pyramids created from age-sex distributions: expansive, constrictive, and stationary. These pyramids are graphical representations of the age and sex distribution of a given population. They are used to determine the stage of development for a given population and to make predictions about the types of services that population will need, such as schools, hospitals, and homes.
Here are the three types of population pyramids:
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Expansive: These pyramids show larger numbers or percentages of the population in the younger age groups, usually with each age group smaller in size or proportion than the one born before it. These types of pyramids are usually found in populations with very large fertility rates and lower than average life expectancies. The age-sex distributions of Latin American and many Third World countries would probably display expansive population pyramids.
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Constrictive: These pyramids display lower numbers or percentages of younger people. The age-sex distributions of the United States and Pennsylvania fall into this type of pyramid. These types of pyramids are generally of the developed countries such as America. They show declining birth rates, low fertility rates, high life expectancy, and low mortality rates. These graphs are narrow at the base and show the decreasing size of the population.
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Stationary: These pyramids show little or no population growth. They are used to describe populations that are neither growing nor shrinking. These pyramids are urn-shaped and are typically representative of developed countries with low birth and death rates.
In summary, the three types of population pyramids are expansive, constrictive, and stationary. Expansive pyramids show larger numbers or percentages of the population in the younger age groups, constrictive pyramids display lower numbers or percentages of younger people, and stationary pyramids show little or no population growth.
