手法を比較

	Voting Power Index Analysis	Two-Level Game Analysis
分野	Political Science	Political Science
系統	MCDM	MCDM
提唱年	1954	1988
提唱者	Lloyd Shapley & Martin Shubik; John F. Banzhaf III	Robert D. Putnam
種類	Cooperative game-theoretic measure of a priori voting power	Framework for analyzing international negotiation under domestic constraints
原典	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.	Putnam, R. D. (1988). Diplomacy and Domestic Politics: The Logic of Two-Level Games. International Organization, 42(3), 427-460.
別名	Voting Power Index, Shapley-Shubik Index, Banzhaf Power Index, A Priori Voting Power Analysis	Two-Level Games, Putnam Two-Level Game Framework, Win-Set Analysis, Double-Edged Diplomacy
関連	4	4
概要	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.	Two-level game analysis is a framework introduced by Robert Putnam in 1988 for understanding how international negotiations are jointly shaped by bargaining between governments and the need to win domestic approval. A negotiator plays simultaneously at two tables: Level I, where states bargain over an agreement, and Level II, where that agreement must be ratified by domestic constituents. The key analytic device is the win-set — the set of Level I deals that could secure domestic ratification — and an agreement is possible only where the negotiating states' win-sets overlap.