Malthus’s theory of population growth – outlined in his Essay on Population (1798) – was a rather pessimistic one. He argued that human populations tend to grow at a much faster rate than the rate at which the means of human subsistence (especially food, but also clothing and other agriculture-based products) can grow.

Therefore humanity is condemned to live in poverty forever because the growth of agricultural production will always be overtaken by population growth. While population rises in geometric progression (i.e., like 2, 4, 8, 16, 32 etc.), agricultural production can only grow in arithmetic progression (i.e., like 2, 4, 6, 8, 10 etc.). Because population growth always outstrips growth in the production of subsistence resources, the only way to increase prosperity is by controlling the growth of the population. Unfortunately, humanity has only a limited ability to voluntarily reduce the growth of its population (through ‘preventive checks’ such as postponing marriage or practising sexual abstinence or celibacy). Malthus believed therefore that ‘positive checks’ to population growth – in the form of famines and diseases – were inevitable because they were nature’s way of dealing with the imbalance between food supply and increasing population.

The modern formulation of the Malthusian theory

The modern formulation of the Malthusian theory was developed by Qumarul Ashraf and Oded Galor. Their theoretical structure suggests that as long as:

(i) higher income has a positive effect on reproductive success, and

(ii) land is the limiting factor of production, then technological progress has only a temporary effect on income per capita. While in the short-run technological progress increases income per capita, resource abundance created by technological progress would enable population growth, and would eventually bring the per capita income back to its original long-run level.

The testable prediction of the theory is that during the Malthusian epoch technologically advanced economies were characterized by higher population density, but their level of income per capita was not different from the level of societies that are technologically backward.