But this belief is often based on state interests. A large population is good because it provides conscripts and cannon fodder for the state in times of war. And a growing population generates new taxpayers to finance social programs for the elderly such as Social Security and Medicare.

On the other hand, since the 1970s, environmentalists have been recycling Thomas Malthus’s arguments to claim that population stagnation or decline would be good because it would prevent or reverse environmental catastrophes. In his 1968 book The Population Bomb, Stanford biologist Paul Ehrlich warned that an exploding world population was hitting resource constraints and that, within a decade, food and water scarcity would result in a billion or more people starving to death. Governments, he opined, should work toward an optimal world population of 1.5 billion, a goal corresponding to 57 percent less than the actual population in 1968 and 81 percent less than today’s 7.9 billion. In 1965, the New Republic announced that the “world population has passed food supply,” and that world hunger would be “the single most important fact in the final third of the 20th Century.” The “freedom to breed is intolerable,” ecologist Garrett Hardin pontificated. Of course, those grim predictions haven’t borne out.

Better arguments / Economics and philosophy offer analyses of population size and growth that are preferable to simplistic governmental and environmentalist viewpoints.

A major economic argument in support of population growth is that, ceteris paribus, more humans mean more trading partners and thus better opportunities for all. The late economist Julian Simon offered a related argument that more people increase the flow of human ingenuity, inventions, and new solutions for human problems.

In the field of religious ethics, Christianity and perhaps especially Catholicism have preached that married couples have a moral duty to engage in the creation of human beings with immortal souls. The larger the population, the better. One corollary seems to be that women should spend their fertile years having babies. At least in advanced countries, few individuals would now agree with that. Demographer Lyman Stone of the Institute for Family Studies defends a less demanding but still nativist Catholic doctrine: “More babies would be good,” he writes, and “a genuinely novel political project” to that effect is needed.

Borrowed from a field of philosophy called population ethics, a secular and utilitarian argument has somewhat similar implications. Some philosophers have argued that a potential individual who is not born amounts to lost utility in the world, and this potential loss must count against the utility gained otherwise—say, by current consumers whose goods produce climate change. A philosophical counterargument to this is that a non-existent individual cannot be included in any utility calculus because there is no “he” (or “she”) to include. Moreover, the number of non-existent individuals potentially to be born is conceptually infinite. And people who make “potential persons” arguments often seem to consider only some potential individuals. Perhaps their invocation of “our children” refers mainly to only “my” children and descendants.

Economics constrains ethics / Economic theory seriously challenges the moral utilitarian argument for population growth, as well as any such argument for limiting population. One insuperable difficulty is that utility is subjective—in the head of each individual—and it is impossible to add up utilities across individuals in an effort to, say, maximize total social utility. Economists say that interpersonal comparisons of utility are scientifically impossible. (See “The Future of Economics in the 1930s,” Winter 2021–2022.) Philosophers may propose moral judgements that make some interpersonal utility comparisons possible, but if the latter are used by governments to impose compulsory controls, they are nothing more than the dictates of philosopher-kings.

Even if such utility calculations were theoretically possible or philosophically desirable, it would remain impossible to find the information they require about future conditions and consequences, which are shrouded in radical uncertainty. The assumption that the political authorities in charge of coordinating the level of population would be able and rightly motivated to perform such calculations is completely unrealistic.

The following illustration may be useful. If a couple increase by two (one boy and one girl) the number of their children, and those additional children and their descendants join with others to form stable couples who have two children each, the population will increase by about 32 persons (25) in four generations, roughly a century. If all families have two additional children, the population will greatly increase. Many people would assume this is good. But then, one of these new individuals may be a second Hitler and cause the killing of 50 million soldiers and civilians in a single generation. We do not and cannot know. Yet, economic and political theory and historical experience very strongly suggest that attempting to eliminate the possibility of such dangerous births would require a government with as much power as Hitler!

As for the religious argument for more babies, it is difficult to discuss rationally if it depends on faith.

Individual or collective choices / There is no reason to believe that the size of mankind should be the province of collective choices—which are, in practice, government choices. The only philosophical case for a collective choice, perhaps, would arise if mankind were in danger of imminent extinction. Like in so many other areas, economics (albeit with some minimal value judgements of the sort “live and let live”) suggests that a superior alternative is usually available: individual choices in a general context of liberty. Let each potential parent decide, or agree on, what will be the number of his or her own children. These individual choices should determine the number of humans, instead of a certain group of individuals “collectively” deciding how many children families should have.

The Chinese experience in population planning shows how collective choices are not a paragon of rationality and nirvana. They are likely to have consequences that are later judged detrimental by many or most people and even by the government itself. China’s decades-long limitation of one child per family has distorted the country’s gender ratio in favor of boys because many parents aborted their first baby or committed infanticide when they discovered it was a girl. That now means that many Chinese men are being left out of the marriage market. Since 2021, the restriction has been eased to allow up to three children per family, but the reality of direct government intervention in family planning remains.

To summarize and conclude: From an economic viewpoint, population growth is not intrinsically good as state interest requires, nor is it intrinsically bad as the environmentalist vulgate decrees. It is a good guess that the more numerous is mankind, the larger the opportunities for beneficial exchange, which includes all sorts of voluntary relations between individuals. Population ethics cannot rely on interpersonal comparisons of utility, except if its pronouncements are meant as mere moral advice. The usefulness of such pronouncements is further limited by the inherent uncertainty of the future. Population matters should thus be left in the domain of individual choices, informed by people’s preferences and moral values.

Readings

• “Neo-Malthusianism and Coercive Population Control in China and India,” by Chelsea Follett. Cato Institute Policy Analysis no. 897, July 21, 2020.
• Selfish Reasons to Have More Kids, by Bryan Caplan. Basic Books, 2011.
• “Should We Care about People Who Need Never Exist?” The Economist, December 20, 2022.
• “The Truth about Demographic Decline,” by Lyman Stone. Law & Liberty, January 2, 2023.
• The Ultimate Resource, by Julian L. Simon. Princeton University Press, 1981.