(a) Rapidly growing population. It has high birth rate and low death rate, so there are more number of young individuals in the population. According to a recent survey, more than 42% of the Indian population consists of children below the age of 14 years, so Indian population is called young population.

Age structure of hypothetical populations which are expected to increase, remain stable or decline with the passage of time.

(b) Stationary population. It has equal birth and death rates, so population shows zero population growth.

(c) Declining population. It has higher death rate than birth rate, so the population of young members is lower than that of old members.