方法对比

	Voting Power Index Analysis	Spatial Voting Model
领域	Political Science	Political Science
方法族	MCDM	MCDM
起源年份	1954	1957
提出者	Lloyd Shapley & Martin Shubik; John F. Banzhaf III	Harold Hotelling, Duncan Black & Anthony Downs
类型	Cooperative game-theoretic measure of a priori voting power	Formal model of electoral and legislative choice
开创性文献	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.	Downs, A. (1957). An Economic Theory of Democracy. Harper & Row. ISBN: 9780060417505
别名	Voting Power Index, Shapley-Shubik Index, Banzhaf Power Index, A Priori Voting Power Analysis	Spatial Theory of Voting, Downsian Model, Proximity Voting Model, Median Voter Model
相关	4	4
摘要	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.	The spatial voting model represents voters and political alternatives as points in a common geometric policy space and assumes that each voter supports the alternative nearest to their own ideal point. Rooted in Hotelling's location theory, Duncan Black's 1948 single-peakedness result, and Anthony Downs's 1957 economic theory of democracy, the model yields two foundational results: the median voter theorem, which identifies the equilibrium policy in one dimension, and the Downsian prediction that two vote-seeking parties converge toward the center. It is the workhorse formalism behind modern empirical estimation of political positions.