Glossary · Game Theory
Incentive Compatibility
also: incentive-compatible · strategy-proof · strategy-proofness · truthful mechanism · revelation principle
Definition
A mechanism is incentive compatible when each participant's best response is to reveal their private information truthfully. The revelation principle (Myerson 1979) shows any equilibrium outcome of any mechanism can be reproduced by a direct, truthful one, which is why marketplace design can restrict attention to rules under which honesty is the dominant or the Bayesian best strategy.
Two strengths of the property are in common use. Dominant-strategy incentive compatibility, also called strategy-proofness, means truth-telling is optimal no matter what others do; the Vickrey auction and deferred-acceptance matching satisfy it. Bayesian incentive compatibility only requires truth-telling to be optimal in expectation given beliefs about others, which is weaker but often the most a designer can get. The concept is the sharpest available test for product mechanics: if a rating prompt, a bidding interface, a self-reported preference survey, or a cancellation-reason form rewards misreporting, the data it produces is a record of strategy rather than of preference, and every model trained on it inherits the distortion.
Essays on this concept
- Game Theory
Mechanism Design for Marketplaces: Incentive Compatibility as a Product Requirement
Ratings, reviews, rankings, and fees are mechanisms, and users play them. eBay feedback ran 99.3% positive while 3.39% of sales went bad. Incentive compatibility is the test, and it belongs in the spec.
- Game Theory
Auction Theory for Ad Buyers: What the Death of Second-Price Means for Bidding
Media buyers learned to bid their true value in a second-price world. Programmatic display switched to first-price in 2019, and search was never truthful. The mechanism decides who keeps the margin.
- Marketing Strategy
Principal-Agent Problems Inside the Growth Organization: Incentive Design for Sales, Agencies, and Attribution
A growth organization is a stack of principal-agent contracts: CMO to sales, company to agency, team to attribution model. All three fail the same three ways, and the fixes are contract design, not culture.
- Game Theory
The Prisoner's Dilemma of Discounting: Why Every Retailer Promotes and Nobody Wins
Persistent discounting is not a marketing failure but an equilibrium. Varian, Lal, and the folk theorem explain why every retailer promotes, and why P&G and J.C. Penney could not simply stop.
- Digital Economics
The Micro-Economics of API Pricing: Marginal Cost, Value Capture, and Developer Elasticity
An API call costs fractions of a cent to serve but can generate thousands in downstream value. The gap between marginal cost and captured value is where the entire API economy lives, and most companies price this gap wrong.
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Authoritative references