Common-pool resource

Some resources are owned by no one yet used up by everyone, and that awkward combination makes them peculiarly hard to manage. Those are common-pool resources.

A common-pool resource is one from which it is difficult to exclude users but whose use by one person reduces what is available to others. This combination, non-excludable like a public good but rival like a private one, makes such resources especially prone to overuse and depletion, the classic setting for the tragedy of the commons.

The awkward combination

Common-pool resources sit between public and private goods. Like public goods, they are non-excludable: it is hard or impossible to keep people from using them. But unlike public goods, they are rival, or subtractable: every unit one person takes is a unit no longer available to anyone else. Fisheries, groundwater, forests, grazing land, and the atmosphere's capacity to absorb pollution are common-pool resources. The difficulty of excluding users, combined with the fact that use depletes the resource, is what makes them so hard to sustain.

Prone to depletion

Because users cannot be excluded but their use diminishes the resource, common-pool resources invite the tragedy of the commons: each user gains from taking more, while the cost of depletion is shared by all, so the resource is overused and can collapse. Overfished seas, exhausted aquifers, and deforested land are the visible results. The incentive facing each individual, to take while the taking is good, runs against the collective interest in preserving the resource, and without some restraint the resource is degraded or destroyed.

Governing the commons

The pessimistic conclusion that common-pool resources are doomed without privatisation or state control was challenged by Elinor Ostrom, who won a Nobel prize for showing that communities frequently govern such resources sustainably through their own rules. Studying fisheries, forests, and irrigation systems, she found that user communities often craft effective arrangements, clear boundaries, agreed rules, monitoring, graduated sanctions, and ways to resolve disputes, that conserve the resource without either privatising it or imposing outside authority. The commons can be governed, given the right institutions.

The common-pool resource is a vital category for understanding environmental and resource problems, capturing the difficult goods that are everyone's to use and no one's to protect. Its tendency toward depletion explains many of the gravest challenges of resource management, while Ostrom's work offers hope, demonstrating that the tragedy is not inevitable and that communities can, with well-designed institutions, govern their commons sustainably.