Measuring Political Power: Explorations of Public Good Power Indices

What do the UN Security Council, the Electoral College and a company\u27s board of directors have in common? They are weighted voting systems, in which voters may have different numbers of votes, and a quota must be met in order to make a decision. However, actual power is not directly proportional to the number of votes held. The common good power index measures power by counting the number of times that a voter appears in ``minimum winning coalitions\u27\u27: groups of voters that have quota, but would lose quota if any member exited the coalition. This measure of power is motivated by the observations that: a) coalitions larger than minimum winning coalitions rarely form and b) all members of a minimum winning coalition are equally necessary. We will explore some aspects of the common good power index