CIRJEF149  "Direct Mechanisms, Virtual Implementation, and MajorityProofness" 
Author Name  Matsushima, Hitoshi 
Date  April 2002 
Full Paper  PDF file@ 
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Abstract 
We investigate implementation in the complete information environments, where a social choice function is defined as a mapping from states to lotteries, and there exist four or more agents. We assume that for every agent, any pair of distinct states induces distinct strict preference orderings over all pure alternatives. In contrast to the previous works, we construct only direct mechanisms. Without any help of mechanism complexity, we can show that every social choice function is virtually implementable, provided that the set of states is restricted in ways that there always exist a majority of agents who dislike a particular agent's dictatorial choice the worst.
