Abstract
We study the complexity of the following problem: Given two weighted voting games G′ and G′′ that each contain a player p, in which of these games is p’s power index value higher? We study this problem with respect to both the Shapley-Shubik power index [16] and the Banzhaf power index [3,6]. Our main result is that for both of these power indices the problem is complete for probabilistic polynomial time (i.e., is PP-complete). We apply our results to partially resolve some recently proposed problems regarding the complexity of weighted voting games. We also show that, unlike the Banzhaf power index, the Shapley-Shubik power index is not #P-parsimonious-complete. This finding sets a hard limit on the possible strengthenings of a result of Deng and Papadimitriou [5], who showed that the Shapley-Shubik power index is #P-metric-complete.
This is a preview of subscription content, log in via an institution.
Buying options
Tax calculation will be finalised at checkout
Purchases are for personal use only
Learn about institutional subscriptionsPreview
Unable to display preview. Download preview PDF.
References
Bachrach, Y., Elkind, E.: Divide and conquer: False-name manipulations in weighted voting games. In: Proceedings of the 7th International Conference on Autonomous Agents and Multiagent Systems, May 2008 (to appear, 2008)
Balcázar, J., Book, R., Schöning, U.: The polynomial-time hierarchy and sparse oracles. Journal of the ACM 33(3), 603–617 (1986)
Banzhaf, J.: Weighted voting doesn’t work: A mathematical analysis. Rutgers Law Review 19, 317–343 (1965)
Bovet, D., Crescenzi, P.: Introduction to the Theory of Complexity. Prentice-Hall, Englewood Cliffs (1993)
Deng, X., Papadimitriou, C.: On the complexity of comparative solution concepts. Mathematics of Operations Research 19(2), 257–266 (1994)
Dubey, P., Shapley, L.: Mathematical properties of the Banzhaf power index. Mathematics of Operations Research 4(2), 99–131 (1979)
Dwork, C., Kumar, R., Naor, M., Sivakumar, D.: Rank aggregation methods for the web. In: Proceedings of the 10th International World Wide Web Conference, pp. 613–622. ACM Press, New York (2001)
Faliszewski, P., Hemaspaandra, L.: The complexity of power-index comparison. Technical Report TR-929, Department of Computer Science, University of Rochester, Rochester, NY (January 2008)
Gill, J.: Computational complexity of probabilistic Turing machines. SIAM Journal on Computing 6(4), 675–695 (1977)
Hemaspaandra, L., Rajasethupathy, K., Sethupathy, P., Zimand, M.: Power balance and apportionment algorithms for the United States Congress. ACM Journal of Experimental Algorithmics 3(1) (1998), http://www.jea.acm.org/1998/HemaspaandraPower
Hunt, H., Marathe, M., Radhakrishnan, V., Stearns, R.: The complexity of planar counting problems. SIAM Journal on Computing 27(4), 1142–1167 (1998)
Krentel, M.: The complexity of optimization problems. Journal of Computer and System Sciences 36(3), 490–509 (1988)
Matsui, Y., Matsui, T.: NP-completeness for calculating power indices of weighted majority games. Theoretical Computer Science 263(1–2), 305–310 (2001)
Papadimitriou, C.: Computational Complexity. Addison-Wesley, Reading (1994)
Prasad, K., Kelly, J.: NP-completeness of some problems concerning voting games. International Journal of Game Theory 19(1), 1–9 (1990)
Shapley, L., Shubik, M.: A method of evaluating the distribution of power in a committee system. American Political Science Review 48, 787–792 (1954)
Simon, J.: On Some Central Problems in Computational Complexity. PhD thesis, Cornell University, Ithaca, N.Y, Available as Cornell Department of Computer Science Technical Report TR75-224 (January 1975)
Toda, S.: PP is as hard as the polynomial-time hierarchy. SIAM Journal on Computing 20(5), 865–877 (1991)
Valiant, L.: The complexity of computing the permanent. Theoretical Computer Science 8(2), 189–201 (1979)
Zankó, V.: #P-completeness via many-one reductions. International Journal of Foundations of Computer Science 2(1), 76–82 (1991)
Author information
Authors and Affiliations
Editor information
Rights and permissions
Copyright information
© 2008 Springer-Verlag Berlin Heidelberg
About this paper
Cite this paper
Faliszewski, P., Hemaspaandra, L.A. (2008). The Complexity of Power-Index Comparison. In: Fleischer, R., Xu, J. (eds) Algorithmic Aspects in Information and Management. AAIM 2008. Lecture Notes in Computer Science, vol 5034. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-68880-8_18
Download citation
DOI: https://doi.org/10.1007/978-3-540-68880-8_18
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-540-68865-5
Online ISBN: 978-3-540-68880-8
eBook Packages: Computer ScienceComputer Science (R0)