Voting Power Index Analysis
Voting power index analysis measures the a priori capacity of each member of a weighted voting body to influence collective decisions, defined as the probability that the member is pivotal — that their vote turns a losing coalition into a winning one. The two canonical indices are the Shapley-Shubik index, introduced by Lloyd Shapley and Martin Shubik in 1954 as a specialization of the Shapley value to simple voting games, and the Banzhaf index, formalized by John Banzhaf in 1965. Both reveal that a player's share of power generally differs sharply from its share of votes.
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Sources
- Shapley, L. S., & Shubik, M. (1954). A Method for Evaluating the Distribution of Power in a Committee System. American Political Science Review, 48(3), 787-792. DOI: 10.2307/1951053 ↗
- Felsenthal, D. S., & Machover, M. (1998). The Measurement of Voting Power: Theory and Practice, Problems and Paradoxes. Edward Elgar. ISBN: 9781858989273
How to cite this page
ScholarGate. (2026, June 22). Voting Power Indices (Shapley-Shubik and Banzhaf). ScholarGate. https://scholargate.app/en/political-science/power-index-analysis
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