Demography is the scientific study of human population. It focuses its attention on the following three observable human phenomenon:
1. Change in population size (growth or decline)
2. Composition of population
3. Distribution of population in space.
The demographic processes which determine these phenomena are:
1. Fertility 2.. Mortality 3. Marriage
4. Migration 5. Social mobility.
A look back into the history shows that every nation passes through five stages of demographic cycle.
1. First stage (High Stationary): It is characterized by high birth rate and high death rate which cancel each other. So the population remains stationary. India was in this stage till 1920.
2. Second stage (Early Expanding): There is a decline in death rate while the birth rate remains unchanged. So the population expands. Many developing countries of Asia and Africa are in this stage.
3. Third stage (Late Expanding): Death rate declines further and birth rate begins to fall. Yet there is an increase in population since birth exceeds deaths. India appears to have entered this stage.
4. Fourth stage (Low Stationary):Low birth rate and low death rate. So the population becomes stationary. Sweden, Belgium, Denmark and Switzerland are in this stage.
5. Fifth stage (Declining): Population begins to decline as birth rate is lower than death rate. East European countries like Germany and Hungary are now in this stage.