Strategy-Proof Aggregation Rules in Median Join-Semilattices and Arrowian Social Welfare Functions
Ernesto Savaglio, Stefano Vannucci · RePEc: Research Papers in Economics · 2020
Three characterizations of the whole class of strategyproof aggregation rules on rich domains of locally unimodal total preorders in Önite 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 Ölters 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.