(a)What is the demographic transition theory? (b) Explain the three stages of the theory.

(a) The demographic transition theory explains the pattern of population change that a country passes through as it develops economically, describing how birth rates and death rates change over time and how this affects the rate of population growth. It states that societies move from a stage of high birth and high death rates, through a stage of falling death rates with still-high birth rates, to a stage of low birth and low death rates.

(b) The three stages:

1. First (high stationary) stage: Both the birth rate and the death rate are high, so they roughly cancel out and the population grows slowly. This is typical of pre-industrial societies with poor medical care, famine and disease.
2. Second (early/late expanding) stage: The death rate falls sharply because of improved medical services, better nutrition, clean water and sanitation, while the birth rate remains high. The wide gap between them causes a rapid increase (population explosion). Many developing countries are in this stage.
3. Third (low stationary) stage: The birth rate also falls, through family planning, urbanisation, education and rising living standards, until it is low and close to the low death rate. Population growth is again slow and the population becomes fairly stable, as in developed countries.