• Historically, India's population was unstable, experiencing fluctuations and occasional declines due to severe famines and deadly pandemics (especially during the 1911–1921 decade).
• Demographers refer to 1921 as the Great Demographic Divide because it is the last census year the country registered a population decline.
• Following 1921, significant improvements in public health, sanitation, and medical facilities caused death rates to drop while birth rates remained high, leading to continuous and rapid growth