A Fast and Simple Algorithm for Computing Market Equilibria

  • Authors:
  • Lisa Fleischer;Rahul Garg;Sanjiv Kapoor;Rohit Khandekar;Amin Saberi

  • Affiliations:
  • Dartmouth College,;IBM T.J. Watson Research Center,;Illinois Institute of Technology,;IBM T.J. Watson Research Center,;Stanford University,

  • Venue:
  • WINE '08 Proceedings of the 4th International Workshop on Internet and Network Economics
  • Year:
  • 2008

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Abstract

We give a new mathematical formulation of market equilibriausing an indirect utility function : the function of pricesand income that gives the maximum utility achievable. Theformulation is a convex program and can be solved when theindirect utility function is convex in prices. We illustrate thatmany economies including Homogeneous utilities of degreeα ∈ [0,1] in Fisher economies — thisincludes Linear, Leontief, Cobb-Douglas Resource allocation utilities like multi-commodityflows satisfy this condition and can be efficiently solved.Further, we give a natural and decentralized price-adjustingalgorithm in these economies. Our algorithm, mimics the naturaltâtonnement dynamics for the markets as suggested by Walras:it iteratively adjusts a good's price upward when the demand forthat good under current prices exceeds its supply; and downwardwhen its supply exceeds its demand. The algorithm computes anapproximate equilibrium in a number of iterations that isindependent of the number of traders and is almost linear in the number of goods. Interestingly, our algorithm applies tocertain classes of utility functions that are not weak grosssubstitutes .