Which of the following is an example of a good that is nonexcludable and rival in consumption?

• A. National defense
• B. Private gym membership
• C. A private park
• D. Public highway

Answer: (D)

Nonexcludable and rival in consumption describes a common-resource type of good. Nonexcludable means you can’t easily prevent people from using it, and rival means one person’s use reduces another’s ability to use it. A public highway fits this well: it’s hard to exclude drivers from using the road, especially without tolls or enforcement, and when traffic is heavy, each additional car reduces space and slows everyone else, so one person’s use diminishes others’ use. By comparison, national defense is nonexcludable and nonrival (a public good), a private gym membership is excludable and rival (a private good), and a private park is excludable (and often rival if capacity is limited). Hence, the public highway is the best example of nonexcludable and rival consumption.