Which characteristic defines public goods?

Public goods are defined by their characteristics of being non-rivalrous and non-excludable. Non-rivalrous means that one person's use of the good does not diminish another person's ability to use it. For example, when a person enjoys a public fireworks display, it doesn't prevent others from enjoying it as well. Non-excludable indicates that it is difficult or impossible to prevent anyone from using the good, making it accessible to everyone regardless of whether they have paid for it. Classic examples of public goods include clean air, national defense, and street lighting.

In contrast, rivalrous goods can become less available as more people use them, whereas excludable goods allow providers to restrict access to those who do not pay. The other options describe private goods or characteristics that do not apply to public goods, thus reinforcing the understanding that public goods occupy a unique position in economics, characterized specifically by their non-rivalry and non-excludability.