The Malthusian population theory, or Malthusianism, says that with high population growth, the food supply could not keep up, creating poverty on a large scale.
This idea was developed during the 18th century by Thomas Malthus, an English economist and clergyman, through the dissemination of his book known as “Essay on the Principle of Population.”
Malthus wanted to explain that the population grew in a geometric progression, while food production and supply had their slowest growth, only by an arithmetic progression.
According to Malthus’ hypothesis, high population growth could make food production unsustainable, as the additional workers would not produce the additional amount needed.
At the time, Malthus argued that there should be a contraceptive method for the poorest people, in order to avoid possible “demographic chaos.” What the economist did not foresee was the arrival of more technology that would allow a much greater food production, avoiding the catastrophe of his theory.
Neo-Malthusianism and other demographic theories
Malthus’s theory appeared during a time when the majority of the population was exchanging the countryside for cities, the main case in England at the end of the 18th century.
Shortly after spreading his theory, Malthus witnessed the Industrial Revolution, which brought more productivity to agriculture with the development of more technology, regardless of Malthus’ hypothesis.
Still, other population theories would appear later, putting world population growth on the agenda in exchange for economic development in addition to food supplies.
This return takes place, even, with the return of Malthusianism in the middle of the 20th century, called Neo-Malthusianism.
Neo-Malthusian theory
With the return of the Malthusian theory, by the neo-Malthusians, the growth of the population in underdeveloped countries was perceived due to the greater access to medical care for these people.
Neo-Malthusian theorists justified that offering more resources to the population would generate higher expenditures for governments, distributing fewer resources in areas where there could be economic growth.
Population theory reform
The reformist theory is approached mainly by the defenders of Karl Marx and socialism, being against neo-Malthusianism. It is also known as anti-Malthusian theory.
For the reformers, overpopulation is generated as a result of poverty due to capitalism, and not as a cause of better economic conditions as advocated by neo-Malthusians.
Because of this, proponents of this theory are in favor of socioeconomic programs improving the living standards of the poorest people.
Demographic transition theory
This theory, developed in the late 1920s, does not agree with previous theories of accelerating population growth.
The idea, in this case, relates the movement of people from the countryside to the city, where the population could have access to better conditions, increasing life expectancy.
The claim is that even with increased life expectancy (reduction in death rates), people would also start to conceive fewer children, which would also lower birth rates.
The process that this theory defends occurs in different phases, which are:
Phase 1: Pre-transition
This is the stage when a country has, in its population, high birth rates and also death rates. This is the case where most people are in the field.
Due to the high birth rate, food production accelerates, but in contrast, medical care and basic sanitation are in short supply, which also increases mortality.
Phase 2: beginning of the transition
Phase in which medical care and basic sanitation improve, mortality rates reduce, and part of the rural population travels to cities.
However, birth rates remain high and the result is an exponential increase in the population.
Phase 3: End of transition.
The end of the transition is the phase in which a good part of the population has already moved to the cities, where they found better socioeconomic conditions and medical care.
This is also the stage, where birth rates begin to decline, and the general level of the population decreases again.
Phase 4: Post-transition
In a more modern model of this theory, a fourth phase has been included where the birth and death rates are low and equivalent.
There may still be a phase after this, where birth rates are below death rates, as a large part of the population chooses to have a small number of children.