Stable Coalition Structures and Power Indices for Majority Voting

Takaaki Abe ()
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Takaaki Abe: School of Political Science and Economics, Waseda University

No 2015, Working Papers from Waseda University, Faculty of Political Science and Economics

Abstract: An (n,k)-game is a voting game in which each player has exactly one vote, and decisions are made by at least k affirmative votes of the n players. A power index is a measure of the a priori power of the n voters. The purpose of this paper is to show what axioms of power indices generate stable coalition structures for each (n,k)-game. Using the stability notion of the core, we show that a coalition structure containing a minimal winning coalition is stable for a wide range of general power indices satisfying a set of axioms, such as the Shapley-Shubik, Banzhaf, normalized Banzhaf, and Deegan-Packel power indices. Moreover, we also show that a coalition structure that represents a two-party system can be stable if the two large parties are close enough in size. Some unstable coalition structures are also analyzed.

Keywords: coalition structure; core; majority voting; power index (search for similar items in EconPapers)
JEL-codes: C71 (search for similar items in EconPapers)
Pages: 18 pages
Date: 2020-10
New Economics Papers: this item is included in nep-cdm, nep-des, nep-gth and nep-pol
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