Theory of Population – SS1 Economics Lesson Note (Second Term)

A theory of population explains how the size of a population changes and what limits it. This note covers two theories: the Malthusian theory, which says population grows faster than food supply until war, disease or famine reduce it, and the demographic transition theory, which describes three stages of birth and death rates in a society.

Behavioural objectives

By the end of the lesson, students should be able to:

• state who wrote the Malthusian theory of population and when;
• list the main features of the Malthusian theory;
• explain the demographic transition theory;
• describe the three stages of the demographic transition theory.

What is the Malthusian theory of population?

The Malthusian theory of population is the outcome of an essay titled ‘An Essay on Population’, written in 1798 by Reverend Thomas Robert Malthus, an Anglican clergyman and a well-known political economist. The essay was influenced greatly by the very fast rate at which the population of Europe was growing at that time. In it, he highlighted the relationship between population and means of subsistence.

What are the main features of the Malthusian theory?

The main views or features of the Malthusian theory about population are:

• Population was growing in a geometric progression such as 2, 4, 8, 16, 32 etc., while food production or supply was growing in an arithmetic progression such as 1, 2, 3, 4, 5 etc.
• There is a tendency for all living things to grow beyond the food available to them.
• Unless population increase is matched with means of subsistence, negative and positive checks will come into force.
• The checks can be war, diseases, epidemics and famine.
• Population is essentially limited by the means of subsistence.

What is the demographic transition theory?

Demographic transition theory is concerned with the historical population growth of a society. It attempts to explain the effect of fertility and mortality on population growth. The theory explains how all developed countries in contemporary times have passed through three identical stages of population history.

What are the stages of the demographic transition theory?

Stage 1: pre-transition stage

This stage is characterised by a high fertility (birth) rate and a high mortality (death) rate.

The population is fairly stable or static, or it decreases or increases at a low rate. It is a feature of a pre-industrial society.

Stage 2: transitional stage

In this stage, both fertility and mortality are declining. Mortality declines more rapidly than fertility at first, and fertility later declines more rapidly, leading to an increase in population. It is a period of population explosion as a result of high birth rates and low death rates. This is a feature of an economy at the industrial take-off, and of a developing economy.

Stage 3: post-transition stage

Both fertility and mortality are low and under control at this stage. The growth rate is controlled and the population remains more or less stable, that is, a period of low birth rate and low death rate which leads to little or no population growth. It is a feature of an advanced economy.

Evaluation

1. Who wrote the essay on which the Malthusian theory is based, and in which year?
2. Explain how Malthus said population and food supply grow.
3. List the checks that Malthus said would come into force if population outgrew food supply.
4. What is the demographic transition theory?
5. State two features of Stage 2 of the demographic transition theory.

Assignment

1. Write short notes on the three stages of the demographic transition theory.
2. Using the numbers 2, 4, 8, 16, 32 and 1, 2, 3, 4, 5, explain the main view of the Malthusian theory.