The case for intellectual property in economic theory notes certain substantial differences from the case for tangible property. Consumption of tangible property is rivalrous. For example, once one person eats an apple, no one else can eat it; if one person uses a plot of land on which to build a home, that plot is unavailable for use by others. Without the right to exclude others from tangible resources, a tragedy of the commons can result. The subjects of intellectual property do not share this feature of rivalness. For example, an indefinite number of copies can be made of a book without interfering with the use of the book by owners of other copies. When combined with a lack of exclusive intellectual property rights, this nonrivalrousness and nonexcludability combine to make them public goods and susceptible to the free rider problem. A rationale for intellectual property therefore rests on incentive effects to overcome the free rider problem. This case asserts that without a subsidy that is afforded by exclusive rights, there is no direct financial incentive to create new inventions or works of authorship.
As Wikipedia and free software demonstrate, works of authorship can be written without direct financial incentives. Moreover, many important works were created before copyright was invented. One might argue that much more invention occurred after patents came into existence; however, one could also argue that patents were brought into law as the power and influence of industrial interests grew. The status of intellectual property is disputed by various commentators in India, China and other developing nations. The United States and the United Kingdom are the only two nations who consistently receive net balance of payment benefits from intellectual property, and are amongst the chief supporters of intellectual property systems.