The year 1921 is referred to as the 'Year of Great Divide' in the demographic history of India. Before 1921, India's population growth was stagnant or even negative in some census periods, primarily due to high death rates from famines, epidemics (like plague and influenza), and poor health conditions. After 1921, the death rate began to decline significantly while the birth rate remained high, leading to a steady and relatively rapid increase in population growth that continued in subsequent decades.