Expected Utility Theory
The standard economic model of rational decision-making under uncertainty, where agents choose options that maximize expected utility.
Also known as: EU Theory, Rational Choice Theory
Category: Decision Science
Tags: economics, decision-making, rationality, game-theory, behavioral-economics
Explanation
Expected Utility Theory (EU theory), developed by von Neumann and Morgenstern in 1944, is the foundational economic model of rational decision-making under uncertainty. According to this theory, a rational agent should choose the option that maximizes expected utility, calculated as the sum of probability times utility across all possible outcomes.
The theory rests on several key assumptions about rational preferences: completeness (agents can compare any two options), transitivity (if A is preferred to B and B to C, then A is preferred to C), continuity, and the independence of irrelevant alternatives. These axioms ensure that preferences can be represented by a utility function.
While EU theory remains normatively powerful - describing how we should ideally make decisions - behavioral economics has shown that humans systematically violate its assumptions. Daniel Kahneman and Amos Tversky's Prospect Theory demonstrated that people are loss-averse, weight probabilities nonlinearly (overweighting small probabilities and underweighting large ones), and evaluate outcomes relative to reference points rather than in absolute terms.
The key differences between Expected Utility Theory and Prospect Theory highlight the gap between rational ideals and actual human behavior: EU assumes linear probability weighting while Prospect Theory shows nonlinear weighting; EU has no reference point while Prospect Theory frames everything as gains or losses from a reference; EU assumes risk neutrality while humans display loss aversion.
Despite its empirical limitations, Expected Utility Theory remains essential in economics, game theory, and decision analysis as a benchmark for rational choice and a tool for prescriptive decision-making.
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