What are public goods identified by?

Public goods are characterized primarily by their non-excludability and non-rivalry. Non-excludability means that once a public good is provided, it is impossible or very costly to exclude individuals from using it. This leads to the "free-rider problem," where individuals may benefit from the good without paying for it. Non-rivalry indicates that one person's use of the good does not reduce the availability of the good for others. For instance, if one person enjoys clean air, it does not diminish the amount of clean air available for others.

These properties necessitate government intervention or collective action, as private markets may fail to provide these goods efficiently, leading to underproduction. Typical examples of public goods include national defense, public parks, and street lighting, where the benefits are shared broadly across society without limiting access for anyone.