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\n\n \n \n Ianovski, E.; and Wilson, M. C.\n\n\n \n \n \n \n \n Manipulability of consular election rules.\n \n \n \n \n\n\n \n\n\n\n
Social Choice and Welfare, 52(2): 363-393. 2019.\n
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@article{ianovski2019manipulability,\n title={Manipulability of consular election rules},\n author={Ianovski, Egor and Wilson, Mark C.},\n journal={Social Choice and Welfare},\n volume={52},\n number={2},\n pages={363-393},\n year={2019},\n publisher={Springer Berlin Heidelberg},\n keywords={social choice, voting},\n url_Paper={https://arxiv.org/abs/1611.07102},\n url_Link={https://link.springer.com/article/10.1007/s00355-018-1152-2},\n abstract={The Gibbard-Satterthwaite theorem is a cornerstone of social choice\ntheory, stating that an onto social choice function cannot be both\nstrategy-proof and non-dictatorial if the number of alternatives is at\nleast three. The Duggan-Schwartz theorem proves an analogue in the case\nof set-valued elections: if the function is onto with respect to\nsingletons, and can be manipulated by neither an optimist nor a\npessimist, it must have a weak dictator. However, the assumption that\nthe function is onto with respect to singletons makes the\nDuggan-Schwartz theorem inapplicable to elections which necessarily\nselect a committee with multiple members. In this paper we make a start\non this problem by considering elections which elect a committee of size\ntwo (such as the consulship of ancient Rome). We establish that if such\na \\emph{consular election rule} cannot be expressed as the union of two\ndisjoint social choice functions, then strategy-proofness implies the\nexistence of a dictator. Although we suspect that a similar result holds\nfor larger sized committees, there appear to be many obstacles to\nproving it, which we discuss in detail.}\n}\n\n
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\n The Gibbard-Satterthwaite theorem is a cornerstone of social choice theory, stating that an onto social choice function cannot be both strategy-proof and non-dictatorial if the number of alternatives is at least three. The Duggan-Schwartz theorem proves an analogue in the case of set-valued elections: if the function is onto with respect to singletons, and can be manipulated by neither an optimist nor a pessimist, it must have a weak dictator. However, the assumption that the function is onto with respect to singletons makes the Duggan-Schwartz theorem inapplicable to elections which necessarily select a committee with multiple members. In this paper we make a start on this problem by considering elections which elect a committee of size two (such as the consulship of ancient Rome). We establish that if such a \\emphconsular election rule cannot be expressed as the union of two disjoint social choice functions, then strategy-proofness implies the existence of a dictator. Although we suspect that a similar result holds for larger sized committees, there appear to be many obstacles to proving it, which we discuss in detail.\n
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\n\n \n \n Hadjibeyli, B.; and Wilson, M. C.\n\n\n \n \n \n \n \n Distance rationalization of anonymous and homogeneous voting rules.\n \n \n \n \n\n\n \n\n\n\n
Social Choice and Welfare, 52(3): 559-583. 2019.\n
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@article{hadjibeyli2019distance,\n title={Distance rationalization of anonymous and homogeneous voting rules},\n author={Hadjibeyli, Benjamin and Wilson, Mark C.},\n journal={Social Choice and Welfare},\n volume={52},\n number={3},\n pages={559-583},\n year={2019},\n publisher={Springer Berlin Heidelberg},\n keywords={social choice, voting},\n url_Paper={https://link.springer.com/content/pdf/10.1007/s00355-018-1156-y.pdf},\n abstract={The concept of distance rationalizability of voting rules has been\nexplored in recent years by several authors. Most previous work has\ndealt with a definition in terms of preference profiles. However, most\nvoting rules in common use are anonymous and homogeneous. In this case\nthere is a much more succinct representation (using the voting simplex)\nof the inputs to the rule. This representation has been widely used in\nthe voting literature, but rarely in the context of distance\nrationalizability. Recently, the present authors showed, as a special\ncase of general results on quotient spaces, exactly how to connect\ndistance rationalizability on profiles for anonymous and homogeneous\nrules to geometry in the simplex. In this article we develop the\nconnection for the important special case of votewise distances,\nrecently introduced and studied by Elkind, Faliszewski and Slinko in\nseveral papers. This yields a direct interpretation in terms of\nwell-developed mathematical topics not seen before in the voting\nliterature, namely Kantorovich (also called Wasserstein) distances and\nthe geometry of Minkowski spaces. As an application of this approach, we\nprove some positive and some negative results about the decisiveness of\ndistance rationalizable anonymous and homogeneous rules. The positive\nresults connect with the recent theory of hyperplane rules, while the\nnegative ones deal with distances that are not metrics, controversial\nnotions of consensus, and the fact that the $\\ell^1$-norm is not\nstrictly convex. We expect that the above novel geometric interpretation\nwill aid the analysis of rules defined by votewise distances, and the\ndiscovery of new rules with desirable properties.}\n}\n\n
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\n The concept of distance rationalizability of voting rules has been explored in recent years by several authors. Most previous work has dealt with a definition in terms of preference profiles. However, most voting rules in common use are anonymous and homogeneous. In this case there is a much more succinct representation (using the voting simplex) of the inputs to the rule. This representation has been widely used in the voting literature, but rarely in the context of distance rationalizability. Recently, the present authors showed, as a special case of general results on quotient spaces, exactly how to connect distance rationalizability on profiles for anonymous and homogeneous rules to geometry in the simplex. In this article we develop the connection for the important special case of votewise distances, recently introduced and studied by Elkind, Faliszewski and Slinko in several papers. This yields a direct interpretation in terms of well-developed mathematical topics not seen before in the voting literature, namely Kantorovich (also called Wasserstein) distances and the geometry of Minkowski spaces. As an application of this approach, we prove some positive and some negative results about the decisiveness of distance rationalizable anonymous and homogeneous rules. The positive results connect with the recent theory of hyperplane rules, while the negative ones deal with distances that are not metrics, controversial notions of consensus, and the fact that the $\\ell^1$-norm is not strictly convex. We expect that the above novel geometric interpretation will aid the analysis of rules defined by votewise distances, and the discovery of new rules with desirable properties.\n
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