Working Paper n.834 - Luglio 2020
DEC, University of Pescara, Italy
Three characterizations of the whole class of strategy-proof aggregation rules on rich domains of locally unimodal total preorders in finite median join-semilattices are provided. In particular, it is shown that such class consists precisely of generalized weak consensus-sponsorship rules induced by certain families of order filters of the coalition poset. It follows that the co-majority rule and many other inclusive aggregation rules belong to that class. The co-majority rule for an odd number of agents is also characterized. The existence of strategy-proof anonymous neutral and unanimity-respecting social welfare functions which satisfy a suitably relaxed independence condition is shown to follow from our characterizations.