Chapter

Algorithms – ESA 2005

Volume 3669 of the series Lecture Notes in Computer Science pp 59-70

On the Price of Anarchy and Stability of Correlated Equilibria of Linear Congestion Games,,

  • George ChristodoulouAffiliated withDepartment of Informatics and Telecommunications, National and Kapodistrian University of Athens
  • , Elias KoutsoupiasAffiliated withDepartment of Informatics and Telecommunications, National and Kapodistrian University of Athens

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Abstract

We consider the price of stability for Nash and correlated equilibria of linear congestion games. The price of stability is the optimistic price of anarchy, the ratio of the cost of the best Nash or correlated equilibrium over the social optimum. We show that for the sum social cost, which corresponds to the average cost of the players, every linear congestion game has Nash and correlated price of stability at most 1.6. We also give an almost matching lower bound of \(1+\sqrt{3}/3=1.577\).

We also consider the price of anarchy of correlated equilibria. We extend existing results about Nash equilibria to correlated equilibria and show that for the sum social cost, the price of anarchy is exactly 2.5, the same for pure and mixed Nash and for correlated equilibria. The same bound holds for symmetric games as well. We also extend the results about Nash equilibria to correlated equilibria for weighted congestion games and we show that when the social cost is the total latency, the price of anarchy is \((3+\sqrt{5})/2=2.618\).