Essays on voting power

This thesis deals with the measurement of voting power in different decision environments. After a short introduction in Chapter 1, several established concepts for power analysis are reviewed and applied in Chapters 2 and 3. Chapters 4 and 5 step on new ground by introducing a power index for a decision environment that has not been formalized before. More specifically, the second chapter contrasts the textbook claim that Luxembourg was a null player in the first period of the European Economic Community (EEC) with a more comprehensive picture of Luxembourg's role in EEC's voting system. It turns out that the assessment of Luxembourg's voting power is sensitive to the role played by the European Commission in the decision-making procedure and to the measurement concepts underlying power evaluations. The third chapter analyzes the European Union's codecision procedure as a bargaining game between the Council of the European Union and the European Parliament. The relative influence of these institutions on legislative decision-making in the EU is assessed under a priori preference assumptions. In contrast to previous studies, the chapter does not consider the codecision procedure in isolation but includes several aspects of the EU's wider institutional framework. The finding that the Council is more influential than the Parliament is robust to adding "context" to the basic model but the imbalance is considerably smaller than was previously diagnosed. The fourth chapter considers collective decisions between more than two alternatives by a given number of differently sized voter groups. Weighted committee games are introduced in order to describe corresponding decision-making in a similar fashion as weighted voting games model binary decision environments. The chapter compares different voting weight configurations for plurality, Borda, Copeland, and antiplurality rule. The respective geometries and distinct numbers of structurally non-equivalent committees have escaped notice so far. Finally, the fifth chapter seeks to clarify if – and quantify the extent to which – adoption of a particular collective choice rule in a weighted committee game creates a (dis)advantage for specific groups a priori. It extends established methods for quantifying influence from weighted voting on binary options to several voting rules for three or more alternatives. Voting weights and decision rules interact in more complicated ways than traditional voting power indices can capture.