What Is Repeated Game?

A comprehensive exploration of repeated games in game theory, including their types, importance, applications, mathematical models, and more.

Definition

A repeated game is a strategic interaction that occurs multiple times, potentially infinitely or finitely. Unlike one-shot games, players in repeated games consider how their current actions affect their reputation and subsequent interactions.

Historical Context

The concept of repeated games emerged from the broader field of game theory, notably developed by John von Neumann and Oskar Morgenstern in the 1940s. Over time, the analysis of repeated games has become critical in understanding strategic behavior in economics, business, and politics.

Types/Categories

Finite Repeated Games

• Description: These games are repeated a known and finite number of times.
• Example: A product pricing game between two competing companies over a holiday season.

Infinite Repeated Games

• Description: These games do not have a predefined endpoint, potentially continuing forever.
• Example: Ongoing trade negotiations between two countries.

Key Events

• 1944: John von Neumann and Oskar Morgenstern introduce game theory in “Theory of Games and Economic Behavior.”
• 1951: John Nash develops the concept of Nash Equilibrium.
• 1971: The Folk Theorem provides critical insights into repeated games.

Detailed Explanations

Equilibrium Strategy in Repeated Games

Players in repeated games have an incentive to build a reputation, impacting their strategy. In finite repeated games, backward induction can be applied, leading to a Nash equilibrium, identical to the one-shot game.

Folk Theorem

The Folk Theorem suggests that multiple equilibrium strategies can exist in infinitely repeated games, offering players various ways to cooperate and benefit in the long run.

Mathematical Formulas/Models

Nash Equilibrium in Finite Repeated Games

For a finite repeated game:

$$ (\sigma_1^*, \sigma_2^*, \ldots, \sigma_N^*) $$

Where \( \sigma_i^* \) is the strategy profile at stage \( i \).

Discounted Repeated Game

When future payoffs are discounted:

$$ \sum_{t=0}^{\infty} \delta^t u_i(a_t) $$

Where \( \delta \) is the discount factor, \( u_i \) is the payoff, and \( a_t \) is the action at stage \( t \).

Charts and Diagrams in Mermaid Format

    graph TD;
	    A(Start) --> B(First Play);
	    B --> C[Strategy Decision];
	    C --> D[Next Round];
	    D --> E{Reputation Assessment};
	    E -->|Good| F[Cooperate];
	    E -->|Bad| G[Defect];
	    F --> D;
	    G --> D;
	    D --> H(End)

Importance

Understanding repeated games is crucial in many fields:

• Economics: To analyze market competition.
• Politics: To understand strategic alliances.
• Business: To model competitive strategies over time.

Applicability

• Trade Negotiations: Countries often engage in repeated games where long-term cooperation is beneficial.
• Price Wars: Businesses may repeatedly engage in pricing strategies to outmaneuver competitors.

Examples

• Tit-for-Tat Strategy: A strategy in repeated games where a player mirrors the opponent’s previous move.
• Prisoner’s Dilemma: When repeated, players may develop trust and cooperation.

Considerations

• Reputation: A key factor, as past actions influence future expectations.
• Strategy Adaptation: Players may change strategies based on previous outcomes.

Related Terms with Definitions

• Game Theory: The study of strategic interactions among rational decision-makers.
• Nash Equilibrium: A concept where no player can benefit by changing their strategy while others keep theirs unchanged.
• Tit-for-Tat: A cooperative strategy in repeated games where players reciprocate actions.

Comparisons

• One-Shot vs. Repeated Games: In one-shot games, reputation does not matter, leading to different strategic choices.
• Finite vs. Infinite Repeated Games: Infinite games allow for more strategies due to the potential for long-term interactions.

Interesting Facts

• Folk Theorem: Named because it was widely known among game theorists before being formally proven.

Inspirational Stories

• Axelrod’s Tournament: Robert Axelrod’s tournaments in the 1980s showed that cooperative strategies like Tit-for-Tat can outperform purely competitive ones.

Famous Quotes

“The key idea of the Folk Theorem is that almost anything can happen.” - Robert Aumann

Proverbs and Clichés

• “What goes around, comes around.”: Reflects the importance of reputation in repeated interactions.

Expressions

• “Playing the long game”: Focusing on long-term benefits over immediate gains.

Jargon and Slang

• “Iterated Prisoner’s Dilemma”: Refers to repeated instances of the Prisoner’s Dilemma game.

FAQs

What is a repeated game?

A game that is played multiple times, with players considering their future interactions.

How does a repeated game differ from a one-shot game?

In repeated games, players consider the long-term effects of their actions, whereas, in one-shot games, they focus only on the immediate payoff.

What is the Folk Theorem?

It states that multiple equilibria can exist in infinitely repeated games, allowing for diverse strategies.

References

• von Neumann, J., & Morgenstern, O. (1944). Theory of Games and Economic Behavior.
• Nash, J. (1951). Non-Cooperative Games. Annals of Mathematics.
• Axelrod, R. (1984). The Evolution of Cooperation.

Summary

Repeated games are fundamental in understanding strategic behavior in various fields. By considering the long-term implications of their actions, players can develop complex strategies that promote cooperation and optimize outcomes over time. This comprehensive understanding of repeated games enhances our ability to analyze and predict behavior in competitive environments.