Tragedy of the Commons

In a 1968 article in Science, Garrett Hardin described what has become one of the lasting metaphors of the twentieth century. Imagine a group of cattle herders surrounding a pasture. No particular herder owns the pasture. Instead, it is common property open to all for grazing their privately owned cattle. The resources of the pasture are finite. It can support the cattle up to a point, but if its carrying capacity is exceeded, the ability to graze any cattle there is soon lost. The herders' problem is to ensure they do not overexploit the resource. This image of free agents surrounding a common and finite resource sets the stage for what has become known as the tragedy, or problem, of the commons.

[Page 1398]The tragedy of the commons develops when individuals take actions that benefit them individually, but that have collectively disastrous results. This paradoxical outcome is likely when individuals can gain the full benefit of their actions without having to bear the full costs of those same actions. Returning to the example at hand, as long as the carrying capacity of the pasture is identifiable, the problem of finite resources is not in itself a tragedy. The herders must simply keep the size of their herds below the pasture's limit. The tragedy develops from communal ownership, which allows each individual to share the costs of additional cattle with all herders surrounding the pasture. With each new animal added to a herd, the new owner gains the full benefit of the addition: using the animal's products, breeding it, selling it at a profit. Each additional animal also exacts a price from the pasture's resources—in grass, water, and fence damage, for example—but this cost does not accrue to its owner alone. Instead, that cost is distributed among all the herders who share the pasture. For individual herders, the benefits of building their herds exceed the individual costs of each additional animal. As individual herders pursue their own rational self-interest, the pasture is soon overexploited. Hardin's view of the problem of the commons follows from marginal utility theory in economics, which assumes that all outcomes follow from the actions of rational, cost-benefit-maximizing individuals. This theory leads to inevitable tragedy: “Ruin is the destination toward which all men rush, each pursuing his own best interest in a society that believes in the freedom of the commons” (Hardin 1968, p. 1244).

From this view, two theoretical solutions to the problem of the commons follow. The first proposes the commons be privatized, that is, that the pasture be divided among the herders for private ownership. With individual private property rights, each herder must now bear the full costs of his actions. The second solution proposes ceding full authority of management of the commons to an external body, usually the state.