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.

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The demographic processes which determine these phenomena are:

1. Fertility 2.. Mortality 3. Marriage

4. Migration 5. Social mobility.

Demographic cycle

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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.

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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.