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The Malthusian Theory of Population

Reviewed by Raphael Zeder | Published Sep 15, 2019

The Malthusian theory of population examines the relationship between population growth and food supply. It states that the population grows exponentially, while its food supply only grows at a linear rate. That eventually causes the population to outgrow its food supply, which leads to a Malthusian crisis. The theory is based on an essay on the Principle of Population, written by Thomas Robert Malthus, an English economist, in 1798. In the following paragraphs, we will take a closer look at the reasoning behind this theory and its shortcomings.

Malthusian Theory Explained

The Malthusian theory of population states that the food supply limits the size of the population. That means, the more food is available, the more people can be sustained. However, according to the theory, the population grows faster than its food supply. More specifically, the population grows at a geometric rate (e.g., 10, 20, 40, 80, etc.), while food supply only grows at an arithmetic rate (e.g., 10, 20, 30, 40, etc.).

Malthus assumed that families always have as many children as they can support. That means, whenever the standard of living rises, people will produce more children and the size of families increases. He then pointed out that larger families can produce even more offspring in the following generation, and so on, which causes the population to grow exponentially. For example, if every family had four kids, the population could, in theory, double with every new generation.

Meanwhile, the food supply is limited by the amount of land available and the time the crops need to grow. Thus, Malthus predicted that even with the help of technological advances, it wouldn’t be possible to increase food production beyond a linear growth rate in the long run.

If left unchecked, these different growth rates eventually cause the population to outgrow its food supply (see illustration below). However, because the availability of food necessarily limits the size of the population, this leads to a so-called Malthusian catastrophe (a.k.a., Malthusian crisis or Malthusian crunch) that brings the population back down to its maximum possible size.

Malthusian Theory of Population Illustration

According to Malthus, two types of checks can keep the population growth in line with its food supply before and after the point of crisis is reached: (1) preventive checks and (2) positive checks.

1) Preventive Checks

Preventive checks are restrictions that limit the growth of the population by lowering the birth rate. That means they mostly refer to moral restraints that prevent people from having children in the first place (hence the name). Examples of preventive checks include abstinence before marriage, birth control, or delaying marriage and kids until there are sufficient financial means to support them. As the name suggests, preventive checks are usually applied before the point of crisis is reached.

2) Positive Checks

Positive checks are restrictions that limit the growth of the population by increasing the death rate. That means they refer to any kind of crisis or disaster that reduces the population’s average lifespan. Examples of positive checks include poverty, plagues, diseases, famines, wars, and so on. Although they can occur at any time, positive checks are mostly applied once the point of crisis is passed.

Criticism of the Malthusian Theory

The Malthusian theory has been subject to a lot of criticism over the past century. Most of it is revolving around the accuracy of Malthus’ predictions and assumptions.

1) Population Growth

Although the global population has increased significantly over the past centuries, the growth rates in most modern economies have turned out to be much lower than predicted by Malthus. As a result, the standard of living has continued to increase, and the population has yet to outgrow its food production.

2) Food Production

Malthus stated that food production would not keep up with population growth due to the law of diminishing returns in farming and agriculture. However, in the past century, the agricultural sector has seen a significant increase in productivity due to technological progress. Advanced machinery, fertilizers, pesticides, and more resilient seeds have increased food production at a much higher rate than Malthus had predicted.

3) Global Trade

Another aspect the Malthusian theory does not account for is the effects of global trade. Because land is limited, Malthus assumed that food production could not grow beyond an arithmetic rate. However, countries can leverage other resources (e.g., natural resources, technology) and export them in exchange for food. That allows them to increase their food supply significantly without access to additional farmland.

4) Standard of Living

Malthus assumed that an increase in the standard of living would result in an increase in the birth-rate and thus accelerate population growth. However, there is increasing evidence that the contrary may be true. In most modern economies, birth-rates have declined as the standard of living has increased.

4) Calculations

Finally, Malthus did not provide any proof that his assumptions of geometric growth of population and arithmetic growth of food production were accurate. It has often been pointed out that there is, in fact, no reason to believe that population and food supply would follow such a pattern consistently.

In a Nutshell

The Malthusian theory of population examines the relationship between population growth and food supply. It states that the population grows geometrically, while its food supply only increases arithmetically. If left unchecked, this causes the population to outgrow its food supply, which leads to a Malthusian catastrophe. According to Malthus, two types of checks can keep the population growth in line with its food supply: preventive and positive checks. Preventive checks are restrictions that limit the growth of the population by lowering the birth rate. Positive checks are restrictions that limit the growth of the population by increasing the death rate.

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