Voting and Power

“Political science, as an empirical discipline, is the study of the shaping and sharing of power” (Lasswell & Kaplan, 1950). As the quote above suggests, the question of power is central to the analysis of political processes. But what do we mean by power? Can it be measured? This is the purpose of this chapter. We will limit ourselves to the analysis of collective decisions within committees. A committee is a group of decision-makers in which decisions are made according to well-established rules. These rules translate into the list of winning coalitionsWinning coalition, these coalitions of decision-makers who, according to the rules, are able to decide. The set of decision-makers and the list of winning coalitionsWinning coalition define a voting gameVoting game. We do not intend to describe the decision procedures as such: a proposal is put on the table and the question is which subsets of decision-makers, if they agree, can together impose a decision, that is, accept or reject the proposal. Decision-makers do not necessarily have the same weight in the decision-making process. They may have a different number of votes, some may have a veto right and special restrictions may be added, such as, for example, the protection of a minority. A general meeting of shareholders, a parliament (where decision-makers are identified with the parties) and international organizations such as the European Council or the United Nations Security Council, are all examples of such committees. The problem addressed in this chapter is the measurement of the relative power of each member of a committee, beyond the apparent power conferred on them by the rules: we want to measure the ability of each decision-maker to influence the outcome of a vote given the rules in force.