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The complexity of power indices in voting games with incompatible players

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  • Martí Jané Ballarín

    (Universitat de Barcelona)

Abstract

We study the complexity of computing the Banzhaf index in weighted voting games with cooperation restricted by an incompatibility graph. With an existing algorithm as a starting point, we use concepts from complexity theory to show that, for some classes of incompatibility graphs, the problem can be solved efficiently, as long as the players have "small" weights. We also show that for some other class of graphs it is unlikely that we can find efficient algorithms to compute the Banzhaf index in the corresponding restricted game. Finally, we discuss the complexity of deciding whether the index of a player is non-zero.

Suggested Citation

  • Martí Jané Ballarín, 2023. "The complexity of power indices in voting games with incompatible players," UB School of Economics Working Papers 2023/441, University of Barcelona School of Economics.
    • Handle: RePEc:ewp:wpaper:441web
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    File URL: http://hdl.handle.net/2445/193061
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    References listed on IDEAS

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    1. Antônio Francisco Neto & Carolina Rodrigues Fonseca, 2019. "An approach via generating functions to compute power indices of multiple weighted voting games with incompatible players," Annals of Operations Research, Springer, vol. 279(1), pages 221-249, August.
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    7. Benati, Stefano & Rizzi, Romeo & Tovey, Craig, 2015. "The complexity of power indexes with graph restricted coalitions," Mathematical Social Sciences, Elsevier, vol. 76(C), pages 53-63.
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    JEL classification:

    • C71 - Mathematical and Quantitative Methods - - Game Theory and Bargaining Theory - - - Cooperative Games

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