- Demographers often divide India's population history into distinct phases. - The period from 1951 to 1981 is characterized by a rapid decline in the death rate due to improved health and sanitation conditions, while the birth rate remained relatively high. This resulted in a significant increase in the natural growth rate and led to what is often termed the "population explosion" phase in India. - The period before 1921 was a phase of stagnant population growth. - The period from 1921 to 1951 saw steady but moderate growth. - The period after 1981 shows a high growth rate but with a declining trend in birth rates, indicating a slowing down compared to the previous three decades.