Q.Define the Theory of Demographic Transition.

The Theory of Demographic Transition explains how a country's birth and death rates change as it develops economically, moving through distinct stages.

The Theory of Demographic Transition is a description of how a country's population growth pattern changes as its economy develops, based on the observed historical behaviour of birth rates and death rates.

Stage 1 (High Stationary): Both birth rate and death rate are high, so the net growth rate stays low. This is typical of a pre-industrial, agrarian economy with limited health care.

Stage 2 (Early Expanding): The death rate falls sharply because of improvements in medicine, sanitation and food supply, but the birth rate remains high because social attitudes towards family size change more slowly. The gap between the two produces rapid population growth — often called the "population explosion" phase.

Stage 3 (Late Expanding / Low Stationary): The birth rate itself now falls, driven by urbanisation, rising education (especially female education), family planning and the rising cost of raising children in a modern economy. Growth rate falls back to a low, stable level.

India is understood to have moved from Stage 2 towards Stage 3 over the last several decades, which is why its decadal Census growth rate has fallen steadily — from 23.9% in 1981-91 to 21.5% in 1991-2001 to 17.7% in 2001-2011.

Students often confuse the order of the stages, or assume the death rate falls in Stage 1 rather than Stage 2 — remember that the death rate is the FIRST of the two rates to fall as development begins, well before the birth rate follows.