Which year is known as the year of the great divide in the demographic history

Prior to 1921, the course of population growth was undulating (several ups and downs, mainly because of mortality differentials). During 1911-1921, India experienced negative growth rate in her population.

After 1921, Mortality started declining as a result of improvement in public heath measures while, fertility remained unchanged which caused a continuous and rapid increase in population growth rate in upcoming decades.

Hence, 1921 was the year when India moved from stage 1 to stage 2 of demographic transition. Therefore, year 1921 is known as the year of the great divide in the demographic history.