Methoden vergleichen

	Spatial Voting Model	Voting Power Index Analysis
Fachgebiet	Political Science	Political Science
Familie	MCDM	MCDM
Entstehungsjahr	1957	1954
Urheber	Harold Hotelling, Duncan Black & Anthony Downs	Lloyd Shapley & Martin Shubik; John F. Banzhaf III
Typ	Formal model of electoral and legislative choice	Cooperative game-theoretic measure of a priori voting power
Wegweisende Quelle	Downs, A. (1957). An Economic Theory of Democracy. Harper & Row. ISBN: 9780060417505	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.
Aliasnamen	Spatial Theory of Voting, Downsian Model, Proximity Voting Model, Median Voter Model	Voting Power Index, Shapley-Shubik Index, Banzhaf Power Index, A Priori Voting Power Analysis
Verwandt	4	4
Zusammenfassung	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.	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.