Kingmakers and leaders in coalition formation

Brams, Steven J. and Kilgour, D. Marc (2010): Kingmakers and leaders in coalition formation.

Abstract

Assume that players strictly rank each other as coalition partners. We propose a procedure whereby they “fall back” on their preferences, yielding internally compatible, or coherent, majority coalition(s), which we call fallback coalitions. If there is more than one fallback coalition, the players common to them, or kingmakers, determine which fallback coalition will form. The first player(s) acceptable to all other members of a fallback coalition are the leader(s) of that coalition.

The effects of different preference assumption--particularly, different kinds of single-peakedness--and of player weights on the number of coherent coalitions, their connectedness, and which players become kingmakers and leaders are investigated. The fallback procedure may be used (i) empirically to identify kingmakers and leaders or (ii) normatively to select them. We illustrate and test the model by applying it to coalition formation on the U.S. Supreme Court, 2005-2009, which shows the build-up over stages of a conservative coalition that prevailed in nearly half of the 5-4 decisions.

• Item Type: MPRA Paper
• Language: English
• Keywords: coalition formation; fallback procedure; kingmakers; leaders; US Supreme Court
• Subjects: D - Microeconomics > D7 - Analysis of Collective Decision-Making > D72 - Political Processes: Rent-Seeking, Lobbying, Elections, Legislatures, and Voting Behavior; C - Mathematical and Quantitative Methods > C7 - Game Theory and Bargaining Theory; D - Microeconomics > D8 - Information, Knowledge, and Uncertainty > D85 - Network Formation and Analysis: Theory

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