Computing power indices for large voting games

Voting power indices enable the analysis of the distribution of power in a legislature or voting body in which different members have different numbers of votes. Although this approach to the measurement of power has been known for a long time, its application to large games has been limited by the difficulty of computing these indices. This paper presents a new method for computing power indices that combines exact methods with an approximate method due to Owen. This method is of most utility in situations where the number of players is large and the voting weights are concentrated in the hands of a small number of members.