Public good

In economics, a public good is some economic good which possesses two properties:

It is non-rivalrous, meaning that it does not exhibit scarcity, and that once it has been produced, everyone can benefit from it.
it is non-excludable, meaning that once it has been created, it is impossible to prevent people from gaining access to the good.

Public goods are said to be 'pure' when they possess these properties absolutely. In practice, most public goods are impure or are confined to particular localities.

Examples of public goods include defence and Law enforcement, clean air and other environmental goods, or information goods such as software development, authorship and invention.

Public goods provide a very important example of market failure. Because no private organisation can reap all the benefits of a public good which they have produced, economic theory concludes that there will be insufficient incentive to produce it. Consumers will take advantage of public goods, without contributing to their creation. This is called the free rider problem.

One general solution to the problem is for governments to raise taxation to fund the production of public goods. The difficulty is to determine how much funding should be allocated to different public goods, and how the costs should be split (see resource allocation mechanisms, public finance).

Another solution, which has evolved for information goods, is to create intellectual property laws, such as copyright or patents, covering the public goods. These laws attempt to remove the natural non-excludability by prohibiting reproduction of the good. Although they can solve the free rider problem, the downside of these laws is that they are a monopoly (often with significant market power) and (almost always) cause a deadweight loss. Since information goods are naturally a public good, enforcement costs (see Software piracy) are often substantial.