Collective decisions are made in every society. They reflect forms and degrees of democracy and equality, while contributing to a more or less even distribution of a society's welfare. An inquiry into collective decisions and social choice in general raises a number of fundamental questions. Is there a fair and theoretically sound way of aggregating individual preferences into values for society as a whole? Does the majority principle work in practice? How should the results of collective decisions be measured and evaluated? What kinds of decisions are consistent with different schools of moral philosophy? A systematic analysis of issues such as these is precisely what concerns the theory of social choice. It examines fundamental problems related to the design of decisions rules in a democratic society. The theory also has important applications: How should income inequality be measured in a society? Can the distribution of welfare be compared among different societies? What determines or not poverty has been mitigated