Don't count out Malthus

The great demographer and economist Thomas Malthus was 23 years old the last time a British summer was this rain-soaked, which was in 1789. The consequences of excessive rainfall in the late 18th century were predictable. Crops would fail, the harvest would be dismal, food prices would rise and some people would starve. It was no coincidence that the French Revolution broke out the same year.

Nine years after that summer, Malthus published his "Essay on the Principle of Population." We would do well to reread it today. Malthus' key insight was simple but devastating. "Population, when unchecked, increases in a geometrical ratio," he observed. But "subsistence increases only in an arithmetical ratio." In other words, humanity can increase like the number sequence 1, 2, 4, 8, 16

, whereas our food supply can increase no faster than the number sequence 1, 2, 3, 4, 5

We are, quite simply, much better at reproducing than feeding ourselves.

Malthus concluded that there must be "a strong and constantly operating check on population." This would take two forms: "misery" and "vice," by which he meant not only alcohol abuse but also contraception and abortion (he was, after all, an Anglican minister).

I wish I could have a free lunch for every time I've heard someone declare "Malthus was wrong." Superficially, it is true, mankind seems to have broken free of the Malthusian trap. The world's population has increased by a factor of more than six since Malthus' time. Yet the global average daily supply of calories consumed has also gone up on a per capita basis, exceeding 2,700 in the 1990s. In France on the eve of the revolution it was just 1,848.

The conventional explanation for this is the succession of revolutions in global agriculture, culminating in the postwar "green revolution" and the current wave of genetically modified crops. Since the 1950s, the area of the world under cultivation has increased by roughly 11%, while yields per hectare (about 2 1/2 acres) have increased by 120%. Yet these statistics don't disprove Malthus. As he said, food production could increase only at an arithmetical rate, and a chart of world cereal yields since 1960 shows just such a linear progression, from below 1 1/2 metric tons to around 3.

Meanwhile, vice and misery have been operating just as Malthus foresaw. Contraception and abortion have been employed to reduce family sizes. And wars, epidemics, disasters and famines have significantly increased mortality. Together, vice and misery have managed to reduce the rate of population growth from 2.2% annually in the early 1960s to about 1.1% today.