What theory describes how individuals overuse a shared resource for their own benefit, leading to depletion?

The tragedy of the commons describes how individuals overuse a shared resource for private benefit, eventually depleting it for everyone.

The classic example is a pasture open to several herders. Each herder gains by adding one more animal, while the resulting damage to the pasture is spread across all users. Because the private benefit is concentrated but the cost is shared, individually rational decisions can produce a collectively harmful result.

Ecologist Garrett Hardin made the modern phrase famous in a 1968 essay, though related ideas appeared much earlier in discussions of common grazing land. The “commons” means a resource governed by shared access; it does not necessarily mean an unowned resource. Fisheries, groundwater, forests and the atmosphere can all create commons problems.

The concept is often confused with the free-rider problem. Free riding concerns benefiting without contributing, whereas the tragedy of the commons concerns excessive use. Elinor Ostrom’s research showed that communities can sometimes prevent tragedy through rules, monitoring, graduated sanctions and clearly defined membership rather than relying only on privatization or state control.