This volume is intended to provide a broad perspective on collective decision-making, presenting economic and political aspects from both a theoretical and empirical viewpoint. The four chapters in the first section of the book give new results in social choice theory, showing how the arrow impossibility theorem applies in both economic and political decisions, and analyzing generalized Borda voting methods. The second section examines elections and committees, by setting up a formal approach to study the election of a legislature by presenting new experimental work on voting in committees, and by outlining a unified theory of political choice. The third section examines decision-making in multiparty politics (including detailed theoretical and empirical study of a number of democracies). The fourth section on political economy covers interest groups, electoral cycles and a formal discussion of the "general will".