Speaker :  Dr. Anup Pramanik

Abstract:

In this paper, we study social choice functions (SCFs) for choosing between two alternatives. We consider the “full” preference domain which allows for indifference. In this framework, Larsson and Svensson (2006) characterizes unanimous and strategy-proof rules. However, there are many onto and strategy-proof SCFs which are not unanimous. This paper studies the relationship between ontoness and unanimity while analyzing strategy-proof rules in this framework. In particular, this paper shows the following results.

•  Firstly, we characterize the class of onto and strategy-proof rules.
•  Then, we show that unanimity and ontoness are equivalent for pairwise strategy-proof SCFs.
•  Consensus rules are the only onto and strongly group strategy-proof rules (Barber`a et al. (2012), Manjunath (2012) and Harless (2015)). We strengthen this result replacing strongly group strategy-proofness by pairwise strategy-  proofness.

Finally we provide a characterization of strict consensus rules. A strict consensus rule is anonymous, onto and strategy-proof but not unanimous.