Measuring Power in Weighted Majority Games

This paper suggests an indicator of power in weighted majority games. An indicator of power determines the ability of a voter to influence the outcomes of the voting bodies he belongs to. In a weighted majority game each voter is assigned a certain nonnegative real number weight and there is a positive real number quota such that a group of voters can pass a resolution if the sum of the weights of the group members is at least as high as the given quota. The new index is shown to satisfy all the reasonable postulates for an index of voting power. If attention is restricted to weighted majority game only, then this index may be considered as an extension of the Banzhaf-Coleman power indices. Finally, the paper develops an axiomatic charﾭacterization of the new index.