TYPES OF POPULATION PYRAMIDS

THE DIFFERENT TYPES OF POPULATON PYRAMIDS

Population pyramids show the different age groups in both sexes as well as the effects of wars, epidemics, infant mortality and birth policies.

The different population pyramids along time reflect the demographic evolution of a society.

There are three types of population pyramid shapes:

1. Triangular shape shows an expanding population.

2. Bell shape is typical for stable populations.

3. Bulb or urn shape is for a contracting or ageing population.

TRIANGULAR – SHAPED PYRAMID

This type of population corresponds to a young population. The base is very wide due to a high birth rate with a high infant mortality rate. The trunk is narrowing because of mortality rate. The top of the pyramid shows the results of mortality rate, and it is very narrow. Life expectancy is short because of bad nutrition and poor sanitation services.

BELL – SHAPED PYRAMID

This type of pyramid represents an adult population. The base is narrow, and the trunk is larger than the triangular pyramid. This reflects the effects of the fall of the birth rate due to birth control.

The drop of the infant mortality rate enlarges the groups of adult and elderly population. In this type of pyramid, life expectancy is longer.

BULB POPULATION PYRAMID

This type of pyramid shows an ageing population. Its characteristics are:

A very narrow be due to a low infant mortality rate and family planning.
The adult population represents most of the population.
The top of the pyramid is wider than the other types of population pyramids because of the better health services.
Life expectancy is long,