Glossary · Game Theory
Prisoner's Dilemma
also: prisoners' dilemma · prisoner's dilemma game · iterated prisoner's dilemma · repeated prisoner's dilemma
Definition
The prisoner's dilemma is a two-player game in which defection is each player's dominant strategy, yet mutual defection leaves both worse off than mutual cooperation. Devised at RAND in 1950 by Flood and Dresher and named by Albert Tucker, it is the canonical model of price wars, promotional escalation, and any arms race where individual rationality produces collective loss.
The one-shot dilemma has a unique equilibrium, mutual defection, and no amount of communication fixes it because promises are not credible. The repeated version is where the interesting economics lives. Axelrod's 1984 tournaments showed that simple reciprocal strategies such as tit-for-tat sustain cooperation when the shadow of the future is long enough, and the folk theorem generalizes the point: with patient players, cooperation can be an equilibrium of the repeated game. Retail promotion, ad-auction bidding, and feature-parity races are dilemmas of this kind. The diagnostic questions are how often the game repeats, how visible defection is, how fast punishment can follow, and how heavily the players discount the future, because those parameters, not goodwill, determine whether a truce holds.
Essays on this concept
- 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.
- Game Theory
Commitment Devices and Credible Threats: Schelling's Playbook for Pricing and Competitive Strategy
In competitive strategy the scarce resource is credibility, not flexibility. Price-match guarantees, MFN clauses, and capacity bets are commitment devices whose job is to change what rivals believe you will do.
- Pricing Strategy
Discount Engineering: When Promotions Destroy LTV
Discounts can acquire incremental customers or destroy lifetime value, and the difference between the two outcomes is more about who the discount reaches than how deep it goes. A framework for telling them apart.
- Game Theory
Advertising as a Costly Signal: Why Expensive Campaigns Persuade Even When They Say Nothing
Much advertising persuades through its cost, not its message. Separating equilibria explain why brand spend that says nothing still moves demand, and why cutting it to fund performance can break the signal.
Authoritative references