In 1968, Garrett Hardin wrote an influential paper named “The Tragedy of the Commons”. It was published in Science and was kind of a big deal. The paper was about the problem of common resources that can be rationally over-used by individuals such that the resources are destroyed – making everyone worse off. The general idea is a great insight and we can see examples everywhere. People being loud in public spaces, odiferous foods microwaved in the breakroom, spoiled food that remains in the refrigerator. These are relatively innocuous. But more substantial parallels include dumping waste into common water sources, overfishing/hunting, or over-harvesting trees or scavenging in common forests.
The Original Problem
Harden was specifically concerned with human overpopulation. He wrote in the same vein as Paul Ehrlich, who published “The Population Bomb” in the same year. Harden explains that the universe, and earth specifically, only has so much matter and carrying capacity for humans. He left the limiting constraint open. Maybe there would be inadequate clean air, water, nutritious food, etc. The specific inadequacy doesn’t matter, they are all due to the finiteness of our world.
From Hardin’s perspective, there was no natural prophylactic that would prevent us from bumping into the natural and horrifying constraint that inadequate resources would impose. He thought that people would continue to reproduce at greater than replacement rates and death would ensue. He also astutely pointed out that if good people agree to limit their number of offspring, then we will be left with only bad people reproducing. They’d place everyone at risk with their irresponsible, though entirely rational, folly. He concludes that the only hope for humanity is a mutual consent to a coercive entity that would prevent this commons problem of over-reproduction.
The Typical Response and its Shortcoming
The most popular argument against Harden comes from Julian Simon, who argued that humans are the source of innovation and ingenuity and that more humans implies more innovation. Against Paul Ehrlich, Simon famously bet that commodity prices would fall over the course of the 1980s, asserting that human ingenuity would increase abundance.
Putting the wager aside, Simon’s idea that humans figure out ways to make resources more accessible is entirely correct – except for when it isn’t. The Malthusian booms and busts in population and persistent subsistent income levels did occur historically. But it’s been a long time since then. For a few hundred years we’ve had increasing standards of living *and* an increasing population. There are exceptions. There’s been starvation in Venezuela, Cuba, Ethiopia, China, North Korea, and Ukraine. These countries were plenty populous with plenty of human minds to tackle the challenges of scarcity. More people = more abundance isn’t exactly what Julian Simon said, but it’s how a lot of people answer Hardin and Ehrlich’s predictions.
The Better Responses
1) Institutional Details
Simon was correct that more population results in more innovation *in particular institutional contexts*. Specifically, people require an incentive to innovate, economize on resources, and spread the innovations to others. If there is a command-and-control economy, then no such market incentive exists. No modern cases of mass starvation occurred in market economies. When flexible prices and international trade are inaccessible, there is little incentive against hoarding or for supplying more resources to strangers. So long as we have flexible prices and access to international trade, we have incentives to reallocate resources and innovate.
2) Markets & Substitutes
Let’s ignore that Hardin was wrong about his premise of ever-growing population. We have the benefit of hindsight. Rather, even with growing population, the quantity of human-usable resources is not determined separately from the number of people. In fact, they are endogenous to each other such that we will not run out of *any* resource – so long as we have flexible prices and private property. That sounds strong, so let me explain.
Assume a finite resource. If a good becomes more scarce, then the price rises. When the price rises, people find alternatives and substitutes. In this way, the scarce good is *never* exhausted. We may have hit “peak oil” consumption, but we’ll never run out of oil. Natural gas, electricity, and bioplastics can and do replace substantial parts of our demand for oil when the price of oil increases. We switch to more plentiful resources as more scarce resources rise in price. This also means diverting resources into producing substitutes. Maybe we grow more corn and soybeans on land that was once fallow or, less likely, suburban in order to produce more biofuels and bioplastics. We trade-off space and effort for in order to get more of what we want more.
Obviously, that’s a sectoral story. Hardin argued resources broadly would be exhausted or that a specific non-transformable or un-substitutable resources would be exhausted. But even here, prices do their thing. As scarcity increases, so do the prices, increasing the cost of additional children. Families respond to the higher cost by economizing on resource consumption, including having fewer kids. This may sound unrealistic to some. But it is very consistent with the modern trope of young adults waiting to have children until they can afford a car, a house, a retirement account, etc. We are well below carrying capacity of the earth and plenty of people already limit their number of kids due to perceived high costs.
3) Children are Costly and have Positive Externalities
Hardin reasoned that parents would selfishly indulge in reproduction at the cost of humanity. But Steven Landsburg has argued the opposite. Specifically, children are costly to raise. They require time, money, patience, medical care, and loads of resources. The common public expense is education, but that pales in comparison to the time and resources that parents pour into their children. And all of that cost, for what? Ultimately, most children will leave the home and go out into the world, only to love someone who is totally unrelated to their original household! They will provide joy, care, humor, and love to other people who didn’t bear the cost of raising them. Parents bear a larger part of the cost and others get a larger part of the benefit. In this regard, it’s amazing that people have children at all! After all, parents fail to internalize all of the benefits of producing children.
My students always dislike reading Hardin’s paper because the conclusion violates their sense of right and wrong. The best students engage with the logic rather than being distracted by their preference for the conclusion. Hardin was a biologist and not an economist. In some sense he was right that eventually the universe will suffer a heat death due to entropy and no humans will survive. But in the sense that the number of humans will exceed the carrying capacity of the earth, he did not make full use of relevant economics as it existed when he wrote his article.
