Garrett Hardin in the context of Non-excludable

In economics, excludability is the degree to which a good, service or resource can be limited to only paying customers, or conversely, the degree to which a supplier, producer or other managing body (e.g. a government) can prevent consumption of a good. In economics, a good, service or resource is broadly assigned two fundamental characteristics; a degree of excludability and a degree of rivalry.

Excludability was originally proposed in 1954 by American economist Paul Samuelson where he formalised the concept now known as public goods, i.e. goods that are both non-rivalrous and non-excludable. Samuelson additionally highlighted the market failure of the free-rider problem that can occur with non-excludable goods. Samuelson's theory of good classification was then further expanded upon by Richard Musgrave in 1959, Garrett Hardin in 1968 who expanded upon another key market inefficiency of non-excludable goods; the tragedy of the commons.

The tragedy of the commons is the concept that, if many people enjoy unfettered access to a finite, valuable resource, such as a pasture, they will tend to overuse it and may end up destroying its value altogether. Even if some users exercised voluntary restraint, the other users would merely replace them, the predictable result being a "tragedy" for all. The concept has been widely discussed, and criticised, in economics, ecology and other sciences.

The metaphorical term is the title of a 1968 essay by ecologist Garrett Hardin. The concept itself did not originate with Hardin but rather extends back to classical antiquity, being discussed by Aristotle. The principal concern of Hardin's essay was overpopulation of the planet. To prevent the inevitable tragedy (he argued) it was necessary to reject the principle (supposedly enshrined in the Universal Declaration of Human Rights) according to which every family has a right to choose the number of its offspring, and to replace it by "mutual coercion, mutually agreed upon".