Excludability

In economics, a good or service is called excludable if it is possible to prevent people (consumers) who have not paid for it from having access to it. By comparison, a good or service is non-excludable if non-paying consumers cannot be prevented from accessing it.

Definition matrix

	Excludable	Non-excludable
Rivalrous	Private goods food, clothing, cars, parking spaces	Common-pool resources fish stocks, timber, coal
Non-rivalrous	Club goods cinemas, private parks, satellite television	Public goods free-to-air television, air, national defense

Examples

An architecturally pleasing building, such as Tower Bridge, creates an aesthetic non-excludable good, which can be enjoyed by anyone who happens to look at it. It is difficult to prevent people from gaining this benefit. A lighthouse acts as a navigation aid to ships at sea in a manner that is non-excludable since any ship out at sea can benefit from it.

The ease and availability of file sharing technology has made many forms of information, especially music, movies, e-books, and computer software non-excludable. If the content producers want to make their works excludable, they have to use either "copy protection" schemes, or use law enforcement in order to prevent one owner of a copy from being able to share it with others.

An example of an excludable good could be a magazine; people who do not pay for the subscription are mostly excluded from obtaining a copy directly from the publisher. Another case is a pay television subscription, which is excludable but non-rivalrous.

Implications and inefficiency

Public goods will generally be underproduced and undersupplied in the absence of government subsidies, relative to a socially optimal level. This is because potential producers will not be able to realize a profit (since the good can be obtained for free) sufficient to justify the costs of production. In this way the provision of non-excludable goods is a classic example of a positive externality which leads to inefficiency. In extreme cases this can result in the good not being produced at all, or it being necessary for the government to organize its production and distribution.

A classic example of the inefficiency caused by non-excludability is the tragedy of the commons (which Hardin, the author, later corrected to the 'tragedy of the unmanaged commons' because it is based on the notion of an entirely rule-less resource) where a shared, non-excludable, resource becomes subject to over-use and over-consumption, which destroys the resource in the process.

Economic theory

Brito and Oakland (1980) study the private, profit-maximizing provision of excludable public goods in a formal economic model.[1] They take into account that the agents have private information about their valuations of the public good. Yet, Brito and Oakland only consider posted-price mechanisms, i.e. there are ad-hoc constraints on the class of contracts. Also taking distribution costs and congestion effects into account, Schmitz (1997) studies a related problem, but he allows for general mechanisms.[2] Moreover, he also characterizes the second-best allocation rule, which is welfare-maximizing under the constraint of nonnegative profits. Using the incomplete contracts theory, Francesconi and Muthoo (2011) explore whether public or private ownership is more desirable when non-contractible investments have to be made in order to provide a (partly) excludable public good.[3]

gollark: Oh, and why fluorine/lithium/beryllium fuels?

gollark: Ah.

gollark: Oh, and what's the "eutectic NaK alloy"?

gollark: Why molten salt, though, as opposed to some non-salt thing?

gollark: So is there any reason except cost to not do that?

References

Brito, Dagobert L.; Oakland, William H. (1980). "On the Monopolistic Provision of Excludable Public Goods". The American Economic Review. 70 (4): 691–704. JSTOR 1803565.
Schmitz, Patrick W. (1997). "Monopolistic Provision of Excludable Public Goods under Private Information". Public Finance. 52 (1): 89–101.
Francesconi, Marco; Muthoo, Abhinay (2011). "Control Rights in Complex Partnerships" (PDF). Journal of the European Economic Association. 9 (3): 551–589. doi:10.1111/j.1542-4774.2011.01017.x. ISSN 1542-4766.

Types of goods
Public goods Private goods (includes household goods) Common goods Common-pool resource Club goods Anti-rival goods Global public goods Global commons
(Non-)Rivalrous goods and (Non-)Excludable goods
Complementary goods vs. Substitute goods vs. Independent goods
Free goods vs. Positional goods
(Non-)Durable goods Intermediate goods (producer goods) Final goods Capital goods
Inferior goods Normal goods (Necessity goods) Neutral goods Ordinary goods Information goods Giffen goods Luxury goods Veblen goods Superior goods
Search goods (Post-)Experience goods Credence goods
Merit goods Demerit goods
Damaged goods Composite goods Intangible goods