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Demographic Theories

People have tried to explain population growth and decline for centuries. A major topic of controversy today is how to deal with an ever-increasing population. This post will look at several theories that try to address population growth.

Malthusian Theory

Thomas Malthus is famous for claiming that the Earth would lose its ability to sustain an ever-growing population. In his theory, Malthus claims three factors would limit the growth of humans on Earth. These three factors are war, famine, and disease. Malthus defined these three factors as “positive checks” because they increase mortality.

Malthus also defined “preventive checks” or factors that reduced fertility. These factors were birth control and celibacy. As resources were depleted, Malthus theorized that they would begin to fight wars, generally leading to famine and disease. As the fighting over resources continued, people would limit the children they have or even forgo marriage and having children together.


Malthus’s predictions turned out to be incorrect. There have been technological improvements that he could never have foreseen. These improvements in technology have not only increased food production but have also included treatments for diseases that used to kill.

However, Malthus was correct about preventive checks. In the western world and some parts of Asia (Japan, China, Singapore, and Thailand). Fertility rates have plummeted as people focus on careers and other things rather than raising a family. The general trend of the world is an increase in people, but this may change with time.

Zero Population Growth

A variation on Malthus theory was developed by Paul Ehrlich. Ehrlich states that the environment and not food supply is the factor that determines the planet’s population. As more and more people abuse the environment, it endangers the human population.

Ehrlich’s solution to this problem is zero population growth which, as its name implies, that the number of births equals the number of deaths. No practical way has been found to do this, but this demographic theory is often associated with conspiracy theories of how the elite wants to limit population growth.

Cornucopian Theory

The opposite of Malthus and Ehrlich’s position would be cornucopian theory. This theory posits that human ingenuity can resolve whatever problems humans face. It is possible to cite human ingenuity examples that develop after a crisis, such as vaccinations. However, often by the time the breakthrough is implemented, the catastrophe has already done significant damage has already been done.

Not even the Black Death of the medieval period completely wiped out humanity. The cornucopian theory is always correct until something happens on Earth that wipes out human existence.

Demographic Transition Theory

Demographic transition theory takes a modeling approach to demographic change. Population growth follows four predictable stages in this theory, as explained below.

Stage 1: Births, deaths, and infant mortality are high with low life expectancy.

Stage 2: Birth rates are high while infant mortality and death drops with an increase in life expectancy

Stage 3: Birthrates decline for the first time while death rates continue their decline, life expectancy continues to increase

Stage 4: Birth and death rates keep falling, life expectancy peaks, the population stabilizes, and may start to decline.

These stages are often associated with industrialization. Many countries enter stage 2 when they begin to industrialize. A fully developed country is often found in stage 3, while a post-industrial country could be found in stage 4.


The question that perhaps everyone is wondering is perhaps how much more can the population grow on this planet? It may be impossible to know for sure. Every time it appears the Earth has reached its limit, new resources are discovered, and there is a boost in technology that makes it easier to continue life with whatever resources are available. A question such as this is one that experts will wrestle with for a long time.

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