Malthus’s Population Principle Explained
By Frank W. Elwell
This essay is a faithful summary of Malthus’s original 1798 “Principle of Population.” While nothing will substitute for reading the original essay with an open mind, I hope this summary will go some way toward rehabilitating this man’s reputation.
Malthus first points out that human nature being what it is, the passion between the sexes appears to be fairly constant and, if unchecked population will double itself every twenty-five years. "Population, when unchecked, increases at a geometrical ratio. Subsistence increases only in an arithmetical ratio. A slight acquaintance with numbers will show the immensity of the first power in comparison with the second." And this leads to Malthus’s principle of population. Because of this unequal power between production and reproduction, "population must always be kept down to the level of the means of subsistence.” While Malthus was not the first one to notice this, he was the first to inquire into the means by which this leveling of population is achieved. The key word in the principle is “always.” Why then do people insist that Malthus predicts a future of population overshoot and collapse?
Here is the key to that riddle: Malthus made the mistake of illustrating the unequal powers of production and reproduction with a mathematical illustration. He supposes that when unchecked, the earth’s human population would double every twenty-five years (a good estimate consistent with current knowledge). Agricultural production at best, he argues, could not possibly keep pace.
But to make the argument more general and less interrupted by the partial views of emigration, let us take the whole earth, instead of one spot, and suppose that the restraints to population were universally removed. If the subsistence for man that the earth affords was to be increased every twenty-five years by a quantity equal to what the whole world at present produces, this would allow the power of production in the earth to be absolutely unlimited, and its ratio of increase much greater than we can conceive that any possible exertions of mankind could make it. Taking the population of the world at any number, a thousand millions, for instance, the human species would increase in the ratio of—1, 2, 4, 8, 16, 32, 64, 128, 256, 512, etc. and subsistence as—1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. In two centuries and a quarter, the population would be to the means of subsistence as 512 to 10: in three centuries as 4096 to 13, and in two thousand years the difference would be almost incalculable, though the produce in that time would have increased to an immense extent (8-9, emphasis added).
He knows full well that population cannot grow long beyond the means of subsistence (“population must always be kept down to the means of subsistence”), he is simply trying to illustrate to his readers the unequal powers of growth in population and food production and therefore the necessity of checks on population. At one point in the Essay he even states: “I am sufficiently aware that the redundant twenty-eight millions, or seventy-seven millions, that I have mentioned, could never have existed” (63). But for various reasons many critics have taken this mental experiment as the theory of population itself and delight in writing that Malthus was wrong, that overshoot and collapse did not occur. Contrary to popular belief (and the belief of many who should know better), Malthus did not predict a future in which population would outrun food supply and eventually collapse.
Other critics write that Malthus was wrong because he did not take into account the possibility of dramatic increases in the production of food. Many criticize him for not taking into account the revolution in agriculture. But he anticipated this argument as well:
No limits whatever are placed to the productions of the earth; they may increase for ever and be greater than any assignable quantity, yet still the power of population being a power of a superior order, the increase of the human species can only be kept commensurate to the increase of the means of subsistence by the constant operation of the strong law of necessity acting as a check upon the greater power (9-10).
It makes no difference how much productivity increases, Malthus writes, it could not long keep up with unrestrained reproduction. Population must be constantly checked to keep it in line with what the earth can produce. While it has become a commonplace in the literature to claim that increased productivity has disproved Malthus’s main contention of the need for population checks this is simply not the case. Assuming 700 million people at the time of the Essay (an estimate widely reported in the literature, and a 25-year doubling time for unchecked population (what modern demographers call “fecundity”), today’s population would now be close to 48 billion. It is not nearly so high (7 billion as of this writing) because there have been constant checks on population in the last 200 years. While food productivity has increased substantially, it has not (nor could it) increase at the same rate as unchecked population growth. Rather, in accordance with Malthus’s theory, the rise in productivity in the last 200 years has been met by a substantial rise in population a rise that has been truly exponential though far less than potential unchecked growth.
What are these checks that Malthus writes about? They are of two types: “Preventive checks” come into play through the “foresight of the difficulties attending the rearing of a family” (22). They include celibacy, contraception, and various forms of non-procreative sex. “Positive checks,” are the “actual distresses of some of the lower classes, by which they are disabled from giving the proper food and attention to their children” (22). Under this heading Malthus includes extreme poverty, diseases, plague, malnutrition, wars, infanticide, and famine. Positive checks are far more likely to operate within poor populations; preventive checks among the upper classes. In Malthus’s view, both positive and preventive checks—or the ways a people go about controlling their fertility—will greatly impact the rest of the sociocultural system.
Malthus’s principle of population is basically the law of supply and demand applied to the relationships between food production and population growth, which he makes clear time and again throughout the Essay. As the food supply increases, food becomes cheaper, and more children are brought into the world. As there are more mouths to feed, food becomes more expensive, thus causing stress on families, more children dying or steps taken to prevent conception itself. As food prices rise, more land is put under the plow, or greater efforts made in intensifying the production of the land itself.
While Malthus recognized that the relationships among the fertility of people and land are a good deal more complex than this simplified assertion, he maintained there is a recurrent reciprocal relationship between the two. Because of this reciprocal relationship between population and production, over the course of sociocultural evolution, both population and food production have grown in tandem. Periods of increase in food productivity, whether because of the application of technology or the expansion of cultivated land, have been met with expansions of population. Periods of stability in food production, or contraction in productivity, have been marked by the same phenomena in population level.
Because people can reproduce faster than they can increase the production of food, population must always be checked through positive or preventive means. This and nothing more, is Malthus’s “Principle of Population.” Over the course of sociocultural evolution, however, the long-term tendency has been for both productivity and population to intensify. This reciprocal growth, of course, has great effect on other parts of the sociocultural system.
For a more extensive discussion of Malthus’s theories refer to Macro Social Theory by Frank W. Elwell. Also see Sociocultural Systems: Principles of Structure and Change to learn how his insights contribute to a more complete understanding of modern societies.
Elwell, F. (2009), Macrosociology: The Study of Sociocultural Systems. Lewiston: Edwin Mellen Press.
Elwell, F. (2013), Sociocultural Systems: Principles of Structure and Change. Alberta: Athabasca University Press.
Malthus, T. R. (Thomas Robert) (2012-05-12). An Essay on the Principle of Population. Kindle Edition.
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Malthusian Theory of Population
Thomas Robert Malthus was the first economist to propose a systematic theory of population. He articulated his views regarding population in his famous book, Essay on the Principle of Population (1798), for which he collected empirical data to support his thesis. Malthus had the second edition of his book published in 1803, in which he modified some of his views from the first edition, but essentially his original thesis did not change.
In Essay on the Principle of Population,Malthus proposes the principle that human populations grow exponentially (i.e., doubling with each cycle) while food production grows at an arithmetic rate (i.e. by the repeated addition of a uniform increment in each uniform interval of time). Thus, while food output was likely to increase in a series of twenty-five year intervals in the arithmetic progression 1, 2, 3, 4, 5, 6, 7, 8, 9, and so on, population was capable of increasing in the geometric progression 1, 2, 4, 8, 16, 32, 64, 128, 256, and so forth. This scenario of arithmetic food growth with simultaneous geometric human population growth predicted a future when humans would have no resources to survive on. To avoid such a catastrophe, Malthus urged controls on population growth. (See here for graphs depicting this relationship.)
On the basis of a hypothetical world population of one billion in the early nineteenth century and an adequate means of subsistence at that time, Malthus suggested that there was a potential for a population increase to 256 billion within 200 years but that the means of subsistence were only capable of being increased enough for nine billion to be fed at the level prevailing at the beginning of the period. He therefore considered that the population increase should be kept down to the level at which it could be supported by the operation of various checks on population growth, which he categorized as "preventive" and "positive" checks.
The chief preventive check envisaged by Malthus was that of "moral restraint", which was seen as a deliberate decision by men to refrain "from pursuing the dictate of nature in an early attachment to one woman", i.e. to marry later in life than had been usual and only at a stage when fully capable of supporting a family. This, it was anticipated, would give rise to smaller families and probably to fewer families, but Malthus was strongly opposed to birth control within marriage and did not suggest that parents should try to restrict the number of children born to them after their marriage. Malthus was clearly aware that problems might arise from the postponement of marriage to a later date, such as an increase in the number of illegitimate births, but considered that these problems were likely to be less serious than those caused by a continuation of rapid population increase.
He saw positive checks to population growth as being any causes that contributed to the shortening of human lifespans. He included in this category poor living and working conditions which might give rise to low resistance to disease, as well as more obvious factors such as disease itself, war, and famine. Some of the conclusions that can be drawn from Malthus's ideas thus have obvious political connotations and this partly accounts for the interest in his writings and possibly also the misrepresentation of some of his ideas by authors such as Cobbett, the famous early English radical. Some later writers modified his ideas, suggesting, for example, strong government action to ensure later marriages. Others did not accept the view that birth control should be forbidden after marriage, and one group in particular, called the Malthusian League, strongly argued the case for birth control, though this was contrary to the principles of conduct which Malthus himself advocated.
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