Causes and rates of change

The three main causes of population change

• Births - usually measured using the birth rate (number of live births per 1,000 of the population per year).
• Deaths - usually measured using the death rate (number of deaths per 1,000 of the population per year).
• Migration - the movement of people in and out of an area.

Rate of change

Births and deaths are natural causes of population change. The difference between the birth rate and the death rate of a country or place is called the natural increase. The natural increase is calculated by subtracting the death rate from the birth rate.

The rate of natural increase is given as a percentage, calculated by dividing the natural increase by 10. For example, if the birth rate is 14 per 1,000 population, and the death rate is 8 per 1000 population, then the natural increase = 14 - 8 = 6. That is ⁶/₁₀₀₀, which is equal to 0.6 per cent.