What is meant by population pyramid? Explain with the help of examples.

A population pyramid is a graphical representation that shows the distribution of various age groups and gender in a population. Population pyramid for youthful population is shown below:

For example, Niger's population pyramid has mostly aged 15 and under and the majority of the population is under 5 years old, which shows how half of the population dies before they reach 30. But in developed countries like USA, Japan, the decrease in birth rate and death rate have kept the base and top at medium level and life expectancy is higher.