DEMOGRAPHIC TRANSITION MODEL

Population change depends mainly on the balance between the birth rate and the death rate. It is also affected by migration.

Throughout history the world’s population has usually shown a natural increase. Exceptions have occurred:

·         During times of disease (the bubonic plague in the Middle Ages and the HIV/AIDS (Human Immunodeficiency Virus, the virus that causes Acquired Immune Deficiency Syndrome) in present-day southern Africa.

·         As a result of war (western Europe during the two World Wars and in present day in Afghanistan)

·         Due to recent improvements in family planning and female education (either voluntary as in several western European countries or enforcement as with China’s one-child policy).

Demographic transition model

The demographic transition model shows the relationship between birth rates and death rates. It describes how, over a period of time, a sequence of change in population growth rates takes place. The model, which was based on population changes in several industrialised countries in Western Europe and North America, suggested that there were four stages through which all countries will eventually pass.

Stage 1. Here both birth rates and death rates fluctuates at a high level (about 35 per 1000) giving a small population growth.

Birth rates are high because:

• ·         No birth control or family planning
• ·         So many children die in infancy that parents tend to produce more in hope that several will live.
• ·         Many children are needed to work on the land.
• ·         Children are regarded as a sign of virility.
• ·         Religious belief (e.g. Roman Catholics, Muslims and Hindus) encourage large families.

High death rates, especially among children, are due to:

• ·         Disease and plague (bubonic, cholera, kwashiorkor).
• ·         Famine, uncertain food supplies, poor diet.
• ·         Poor hygiene: no piped, clean water and no sewage disposal.
• ·         Little medical science: few doctors, hospitals, drugs.

Stage 2. Birth rates remain high, but death rates fall rapidly to about 20 per 1000 people giving a rapid population growth.

The fall in death rate results from:

• ·         Improved medical care: vaccinations, hospitals, doctors, new drugs and scientific inventions.
• ·         Improved sanitation and water supply.
• ·         Improvements in food production (both quality and quantity)
• ·         Improved transport to move food, doctors, etc.
• ·         A decrease in child mortality.

Stage 3. Birth rates fall rapidly, to perhaps 20 per 1000 people, while death rates continue to fall slightly (15 per 1000 people) to give a slowly increasing population.

The fall in birth rate may be due to:

• ·         Family planning: contraceptives, sterilisation, abortion and government incentives.
• ·         A lower infant mortality rate, therefore less needs to have so many children.
• ·         Increase industrialization and mechanization meaning fewer labourers are needed.
• ·         Increased desire for material possessions (cars, holidays, bigger homes) and less for large families.
• ·         Emancipation of women, enabling them to follow their own careers rather than being solely child bearers.

Stage 4. Both birth rates and death rates remain low, fluctuating slightly to give a steady population.

Nowadays the MEDCs (the more economically developed countries) have reached stage 4 (UK, USA, and Spain). Meanwhile the more developed LEDCs have reached the 3 stage (India, Mexico, Brazil, and the least developed remain al 2 stage (Chad, Nigeria, Kenya).

It has been notice that since the 1990s several MEDCs appear to be entering in a new and fifth stage. This stage is where the birth rate is beginning to fall below the death rate. It is predicted that, if this trend continue, countries entering this stage will eventually see a natural decrease in their total population.