手法を比較

	Collective Action Analysis	Median Voter Model
分野	Political Economy	Political Economy
系統	MCDM	MCDM
提唱年	1965	1948
提唱者	Mancur Olson & Elinor Ostrom	Duncan Black & Anthony Downs
種類	Formal model of group behavior	Formal model of electoral competition
原典	Olson, M. (1965). The Logic of Collective Action: Public Goods and the Theory of Groups. Harvard University Press. ISBN: 9780674537514	Black, D. (1948). On the Rationale of Group Decision-making. Journal of Political Economy, 56(1), 23-34.
別名	Logic of Collective Action, Olsonian Collective Action Theory, Free-Rider Analysis, Group Size and Public Goods Theory	Median Voter Theorem, Black's Median Voter Theorem, Downsian Median Voter Model, Median Voter Equilibrium
関連	4	4
概要	Collective action analysis explains why rational, self-interested individuals will often fail to act together to secure a common interest, even when every member of the group would benefit from doing so. In his 1965 The Logic of Collective Action, Mancur Olson overturned the prevailing assumption that groups with shared interests would naturally organize to advance them, showing instead that because the fruits of collective action are non-excludable public goods, each member has an incentive to free-ride on the efforts of others. The problem worsens as the group grows: large, latent groups chronically undersupply their collective good unless they offer selective incentives or coerce participation, while small, privileged groups can succeed. Elinor Ostrom's 1990 Governing the Commons later documented how communities craft durable institutions that solve such dilemmas without the state or privatization, earning her the Nobel Prize.	The median voter model is a foundational result of political economy stating that, under majority rule with voters whose preferences are single-peaked on a single policy dimension, the ideal point of the median voter is the Condorcet winner — it cannot be beaten by any other alternative in pairwise majority voting. Duncan Black established the theorem formally in 1948, and Anthony Downs extended it in 1957 into a theory of party competition in which two vote-maximizing parties converge to the median voter's preferred policy. The model is the workhorse linking the distribution of citizen preferences to equilibrium policy outcomes in democracies.