The population pyramid (The age-sex pyramid)
The age-sex structure of a population refers to the number of females and males in different age groups. A population pyramid is used to show the age-sex structure of the population. The shape of the population pyramid reflects the characteristics of the population.
The left side shows the percentage of males while the right side shows the percentage of women in each age group. The following three diagrams show different types of Population Pyramids.
Expanding Population
The age-sex pyramid in such a case is a triangular-shaped pyramid with a wide base and is typical of less developed countries. These have larger populations in lower age groups due to high birth rates.
Constant Population
Here, the age-sex pyramid is bell-shaped and tapered towards the top. This shows birth and death rates are almost equal leading to a near-constant population.
Declining Population
This pyramid has a narrow base and a tapered top showing low birth and death rates. The population growth in developed countries is usually zero or negative.
