Explain the tragedy of the commons and how it relates to common resources.

• A. When a non-excludable but rival resource is overused, leading to depletion.
• B. When a good is excludable and non-rival, under-provision occurs.
• C. When government regulation perfectly enforces property rights.
• D. When externalities are completely internalized.

Answer: (A)

The tragedy of the commons occurs when a resource is non-excludable (hard to prevent anyone from using it) and rivalrous (one person’s use reduces what others can use). Each person has an incentive to take as much as possible today because the private benefit of an extra unit goes to the individual while the cost of overuse is shared by everyone. Without clear property rights or coordinated management, this leads to overuse and depletion of the resource, even though everyone would be better off with restraint. This pattern fits common-pool resources like pastures, fisheries, or unregulated groundwater. The other statements describe different kinds of goods or assume perfect regulation or full internalization of externalities, which would mitigate or remove the problem rather than create it.