A Unified Characterization of Randomized Strategy-proof Rules

We show that a large class of restricted domains such as single-peaked, single-crossing, single-dipped, tree-single-peaked with top-set along a path, Euclidean, multi-peaked, intermediate (Grandmont (1978)), etc., can be characterized by using betweenness property, and we present a unified characterization of unanimous and strategy-proof random rules on these domains. As corollaries of our result, we show that all the domains we consider in this paper satisfy tops-onlyness and deterministic extreme point property. Finally, we consider weak preferences and provide a class of unanimous and strategy-proof random rules on those domains.