revealed preference theory

revealed preference theory, in economics, a theory, introduced by the American economist Paul Samuelson in 1938, that holds that consumers’ preferences can be revealed by what they purchase under different circumstances, particularly under different income and price circumstances. The theory entails that if a consumer purchases a specific bundle of goods, then that bundle is “revealed preferred,” given constant income and prices, to any other bundle that the consumer could afford. By varying income or prices or both, an observer can infer a representative model of the consumer’s preferences.

Much of the explanation for consumer behaviour, particularly consumer choice, is rooted in the concept of utility developed by the English philosopher and economist Jeremy Bentham. Utility represents want (or desire) satisfaction, which implies that it is subjective, individualized, and difficult to quantify. By the early 20th century, substantial problems with the use of the concept had been identified, and many proposed theoretical replacements struggled with the same critiques. As a result, Samuelson offered what became known as revealed preference theory in an attempt to build a theory of consumer behaviour that was not based on utility. He argued that his new approach was based on observable behaviour and that it relied on a minimal number of relatively uncontroversial assumptions.

As revealed preference theory developed, three primary axioms were identified: the weak, strong, and generalized axioms of revealed preference. The weak axiom indicates that, at given prices and incomes, if one good is purchased rather than another, then the consumer will always make the same choice. Less abstractly, the weak axiom argues that if a consumer purchases one particular type of good, then the consumer will never purchase a different brand or good unless it provides more benefit—by being less expensive, having better quality, or providing increased convenience. Even more directly, the weak axiom indicates that consumers will purchase what they prefer and will make consistent choices.

The strong axiom essentially generalizes the weak axiom to cover multiple goods and rules out certain inconsistent chains of choices. In a two-dimensional world (a world with only two goods between which consumers choose), the weak and strong axioms can be shown to be equivalent.

While the strong axiom characterizes the implications of utility maximization (see expected utility), it does not address all the implications—namely, there may not be a unique maximum. The generalized axiom covers the case when, for a given price level and income, more than one consumption bundle satisfies the same level of benefit. Expressed in utility terms, the generalized axiom accounts for circumstances where there is no unique bundle that maximizes utility.

The two most-distinguishing characteristics of revealed preference theory are as follows: (1) it offers a theoretical framework for explaining consumer behaviour predicated on little more than the assumption that consumers are rational, that they will make choices which advance their own purposes most efficiently, and (2) it provides necessary and sufficient conditions, which can be empirically tested, for observed choices to be consistent with utility maximization.

P.A. Samuelson, “A Note on the Pure Theory of Consumer’s Behaviour,” Economica, 5(17):61–71 (1938), and “Consumption Theory in Terms of Revealed Preference,” Economica, 15(60):243–253 (1948).