Integer Programming and Combinatorial Optimization

Volume 3509 of the series Lecture Notes in Computer Science pp 167-181

On the Inefficiency of Equilibria in Congestion Games

  • José R. CorreaAffiliated withSchool of Business, Universidad Adolfo Ibáñez
  • , Andreas S. SchulzAffiliated withSloan School of Management, Massachusetts Institute of Technology, Office E53-361
  • , Nicolás E. Stier-MosesAffiliated withGraduate School of Business, Columbia University


We present a short geometric proof for the price of anarchy results that have recently been established in a series of papers on selfish routing in multicommodity flow networks. This novel proof also facilitates two new types of results: On the one hand, we give pseudo-approximation results that depend on the class of allowable cost functions. On the other hand, we derive improved bounds on the inefficiency of Nash equilibria for situations in which the equilibrium travel times are within reasonable limits of the free-flow travel times. These tighter bounds help to explain empirical observations in vehicular traffic networks. Our analysis holds in the more general context of congestion games, which provides the framework in which we describe this work.