Explain the change in the pattern of increase in the growth of population

Explain the change in the pattern of increase in the growth of population during the period 1951-81 and 1981-91.

Population is a dynamic phenomenon. There is a constant change in number, distribution and composition of population. The following points show pattern of population growth in IndiaThe annual growth rate of population from 1951-81 was steadily increasing. It was 1.25% in 1951 and 2.22% in 1981.
Since 1981, the rate of growth of population started declining gradually. The annual growth rate of population in 1981 was 2.22% and it decreased to 2.14% in 1991.