A ranking over opportunity sets is justifiable if there exists a binary relation on the set of alternatives, such that one opportunity set is at least as good as the second, if and only if there exists at least one alternative in the first set which is at least as good as any alternative of the...

Information function method is a powerful tool for analyzing the information requirements of social welfare functions. However, the original information function provides only a coarse description of information structure. In this article, we propose a refinement of this method by changing the...

To examine the consequences of allowing individual to violate full rationality in collective decision making, this article discusses the possibility of aggregating quasi-transitive preferences in the Arrovian framework. Quasi-transitive valued aggregating functions are discussed and...