We propose an aggregation model which explains stereotype formation under the attribution hypothesis. We show, under very mild axioms, that an observer can be thought of perceiving a group in terms of her subjective opinion about the representativeness of subgroups, as well as a possible...

By extending manipulability indices defined for single-valued social choice rules to the multi-valued case, we explore the degree of manipulability of seven multi-valued social choice rules. Our analysis is based on computational experiments.