Malthusianism

One of the first social scientists to tackle the matter of population growth and its consequences was the Englishman Reverend Thomas Robert Malthus (1766–1834), whose famous book Essay on the Principles of Population Growth (published in 1798) electrified the world. Malthus's ideas, contrived in the early days of the Industrial Revolution during the late 18th century, had an enormous impact on political economy and demography. Malthus was concerned with the growing poverty evident in British cities at the time, and his explanation was largely centered on the high rates of population growth that he observed and that are common to early industrializing societies. Thus, it is with Malthus that the theory of overpopulation originated. His pessimistic worldview earned economics the label of the “dismal science.”

The essence of Malthus's line of thought is that human populations, like those of most animal species, grow exponentially (or, in the parlance of his times, geometrically). A geometric series of numbers increases at an increasing rate of time. For example, in the sequence 1, 2, 4, 8, 16, 32, and so on, the number doubles at each time period, and so the increase rises from 1 to 2, to 4, to 8, and so on. Exponential population growth, in the absence of significant constraints, is widely observed in bacteria and rodents, to take but a few examples from zoology. Note that there is an important assumption regarding fertility embedded in Malthus's analysis; he portrayed fertility as a biological inevitability, not as a social construction. This argument was in keeping with the large size of British families at the time. In short, in Malthus's view, humans, like animals, always reproduced at the biological maximum; they were portrayed as prisoners of their genetic urges to reproduce. It is worth noting that Malthus's argument carried with it a strong moral dimension; it was not just anyone who reproduced rapidly, he observed, but most particularly the poor.

Malthus maintained that food supplies, or resources more generally, grew at a much slower rate than did population. Specifically, he held that the food supply grew linearly (or, in his terminology, arithmetically). An arithmetic sequence of numbers, in contrast to an exponential one, grows at a constant rate over time. For example, in the sequence 1, 2, 3, 4, 5, and so on, the difference from one number to the next is always the same. Malthus's view that agricultural outputs increased linearly over time reflected the preindustrial farming systems that characterized his world. In such circumstances, without economies of scale, an increase in outputs is accomplished only with a proportional increase in inputs such as labor, reflective of what economists call a linear production function. However, this view of agricultural output actually is rather optimistic by Malthus's reckoning. He argued that in the face of limited inputs of land and capital, agricultural output was likely to suffer from diminishing marginal returns. For example, as farmers moved into areas that were only marginally hospitable for crops, perhaps because they were too dry, too wet, too cold, or too steep, farmers would need increases in inputs that were proportionately much larger than the increases in output. Diminishing returns, he held, would actually lead to increases in agricultural output that were smaller than those a production system lacking economies of scale would generate.

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