Steven Kivinen (University of Graz) will be presenting his paper “On the Manipulability of Equitable Voting Rules “ on December 13th at 10 AM, room QA 405. One-to-one meetings with the speaker can be arranged; please contact the seminar organizers, Dr. Noémie Cabau (email@example.com) and Dr. Arseniy Samsonov (firstname.lastname@example.org).
We consider the equity-manipulability trade-off when voting over two alternatives. Pairwise equity is a weakening of anonymity requiring certain permutations of the voters’ identities to preserve the outcome of the election. l-robust group strategy-proofness (l-RGSP) and fine robust group strategy-proofness (FRGSP) are notions of group strategy-proofness that allow voters to have different beliefs about players’ types (Kivinen and Tumennasan, 2021). Our main results show that, under mild conditions, for pairwise equitable voting rules anonymity is equivalent to 2-RGSP, 3-RGSP, and FRGSP. In this way, anonymity is special in its equity and non-manipulability. These results follow from several preliminary results, one of which equates 2-RGSP to comonotonicity and swap-robustness. Finally, we consider the manipulability of k-unanimous rules, and 2-RGSP when agents can be indifferent and abstain.