"The probability of coalition formation: Spatial voting power indices"

Bilal, Sanoussi and Albuquerque, Paul and Hosli, Madeleine O. (2001) "The probability of coalition formation: Spatial voting power indices" . In European Union Studies Association (EUSA) > Biennial Conference > 2001 (7th), May 31-June 2, 2001, pages 15, Madison, Wisconsin.

Abstract

This paper aims to include actor’s policy preferences into a probabilistic definition of two common indices of relative voting power: the Shapley-Shubik index and the (normalized) Banzhalf index. While we acknowledge the validity of standard indices and their strength in analyzing relative influence in institutions in an a priori, or ‘constitutional,’ perspective, we develop upon them here in an attempt to explicitly account for players’ policy preferences. Hence, we aim to partially combine spatial approaches of voting with power analysis. After elaborating a respective model for both uni-dimensional and multi-dimensional policy spaces, we suggest ways to test the predictive capacity of such models, either by directly incorporating data on preferences or by estimating such preferences, for example on the basis of theories of endogenous policy formation.