Título: Impartial Social Rankings
Sala: E28
Hora: 12:30
Abstract: We model a situation where a set of selfish agents must rank themselves on the basis of the opinions that they hold regarding the merits of each candidate. Each agent submits her opinion in a message (a nomination, a ranking, a utility function, . . . ). We call the collection of such messages a message profile and this is the input for a social ranking function that determines the final ranking. We are interested in impartial social ranking functions, that is, those where the contribution of a single agent to the social outcome can have no consequence on any social judgment between him and someone else. We obtain two types of results. On the negative side, we show some impossibility results stating the impossibility of combining impartiality with some classical properties of symmetry across agents. On the positive side, we provide two characterizations combining impartiality with weakenings of the main property of symmetry across agents.