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Öğe Approval as an Intrinsic Part of Preference(Springer-Verlag Berlin, 2010) Sanver, M. Remzi[Abstract Not Available]Öğe Arrovian impossibilities in aggregating preferences over non-resolute outcomes(Springer, 2008) Dogan, Emre; Sanver, M. RemziLet A be a set of alternatives whose power set is (A) under bar. Elements of (A) under bar are interpreted as non-resolute outcomes. We consider the aggregation of preference profiles over (A) under bar into a (social) preference over (A) under bar. In case we allow individuals to have any complete and transitive preference over (A) under bar, Arrow's impossibility theorem naturally applies. However, the Arrovian impossibility prevails, even when the set of admissible preferences over A is severely restricted. In fact, we identify a mild regularity condition which ensures the dictatoriality of a domain. Regularity is compatible with almost all standard extension axioms of the literature. Thus, we interpret our results as the strong prevalence of Arrow's impossibility theorem in aggregating preferences over non-resolute outcomes.Öğe Belirsizlik içeren seçenekler üzerindeki tercihlerin incelenmesi(2008) Sanver, M. Remzi[Abstract Not Available]Öğe A characterization of superdictatorial domains for strategy-proof social choice functions(Elsevier Science Bv, 2007) Sanver, M. RemziA domain D is dictatorial iff there exists no surjective, strategy-proof and non-dictatorial social choice function defined over D. A dictatorial domain D is superdictatorial iff every superdomain of D is also dictatorial. The existence of dictatorial but not superdictatorial domains being known, we show that a dictatorial domain D is superdictatorial iff every alternative is ranked at the top by some ordering in D. (C) 2007 Elsevier B.V. All rights reserved.Öğe Characterizations of majoritarianism: a unified approach(Springer, 2009) Sanver, M. RemziDefining regularity as the conjunction of unanimity, anonymity, neutrality and monotonicity, we show that every regular social choice rule can be expressed as a function of vote differences and the maximal number of canceling couples. This equivalence not only identifies the class of regular social choice rules but also allows a unified conception of various majority characterizations.Öğe Choosers as extension axioms(Springer, 2009) Erdamar, Bora; Sanver, M. RemziWe consider the extension of a (strict) preference over a set to its power set. Elements of the power set are non-resolute outcomes. The final outcome is determined by an (external) chooser which is a resolute choice function. The individual whose preference is under consideration confronts a set of resolute choice functions which reflects the possible behaviors of the chooser. Every such set naturally induces an extension axiom (i.e., a rule that determines how an individual with a given preference over alternatives is required to rank certain sets). Our model allows to revisit various extension axioms of the literature. Interestingly, the Gardenfors (1976) and Kelly (1977) principles are singled-out as the only two extension axioms compatible with the non-resolute outcome interpretation.Öğe Computational foundations of social choice(2011) Özkal, İpek Sanver; Aşan, Göksel; Sanver, M. Remzi[Abstract Not Available]Öğe Critical strategies under approval voting: Who gets ruled in and ruled out(Elsevier Sci Ltd, 2006) Brams, Steven J.; Sanver, M. RemziWe introduce the notion of a critical strategy profile under approval voting (AV), which facilitates the identification of all possible outcomes that can occur under AV. Included among AV outcomes are those given by scoring rules, single transferable vote, the majoritarian compromise, Condorcet systems, and others as well. Under each of these systems, a Condorcet winner may be upset through manipulation by individual voters or coalitions of voters, whereas AV ensures the election of a Condorcet winner as a strong Nash equilibrium wherein voters use sincere strategies. To be sure, AV may also elect Condorcet losers and other lesser candidates, sometimes in equilibrium. This multiplicity of (equilibrium) outcomes is the product of a social-choice framework that is more general than the standard preference-based one. From a normative perspective, we argue that voter judgments about candidate acceptability should take precedence over the usual social-choice criteria, such as electing a Condorcet or Borda winner. (c) 2005 Elsevier Ltd. All rights reserved.Öğe Dictatorial domains in preference aggregation(Springer, 2007) Ozdemir, Ugur; Sanver, M. RemziWe call a domain of preference orderings dictatorial if there exists no Arrovian (Pareto optimal, IIA and non-dictatorial) social welfare function defined over that domain. In a finite world of alternatives where indifferences are ruled out, we identify a condition which implies the dictatoriality of a domain. This condition, to which we refer as being essentially saturated, is fairly weak. In fact, independent of the number of alternatives, there exists an essentially saturated ( hence dictatorial) domain which consists of precisely six orderings. Moreover, this domain exhibits the superdictatoriality property, i.e., every superdomain of it is also dictatorial. Thus, given m alternatives, the ratio of the size of a superdictatorial domain to the size of the full domain may be as small as 6/m!, converging to zero as m increases.Öğe Ensuring pareto optimality by referendum voting(Springer, 2006) Ozkal-Sanver, Ipek; Sanver, M. RemziWe consider a society confronting the decision of accepting or rejecting a list of (at least two) proposals. Assuming separability of preferences, we show the impossibility of guaranteeing Pareto optimal outcomes through anonymous referendum voting, except in the case of an odd number of voters confronting precisely two proposals. In this special case, majority voting is the only anonymous social choice rule which guarantees Pareto optimal referendum outcomes.Öğe Expected Utility Consistent Extensions of Preferences(Springer, 2009) Can, Burak; Erdamar, Bora; Sanver, M. RemziWe consider the problem of extending a (complete) order over a set to its power set. The extension axioms we consider generate orderings over sets according to their expected utilities induced by some assignment of utilities over alternatives and probability distributions over sets. The model we propose gives a general and unified exposition of expected utility consistent extensions whilst it allows to emphasize various subtleties, the effects of which seem to be underestimated - particularly in the literature on strategy-proof social choice correspondences.Öğe A general impossibility result on strategy-proof social choice hyperfunctions(Academic Press Inc Elsevier Science, 2009) Ozyurt, Selcuk; Sanver, M. RemziA social choice hyperfunction picks a non-empty set of alternatives at each admissible preference profile over sets of alternatives. We analyze the manipulability of social choice hyperfunctions. We identify a domain D-lambda of lexicographic orderings which exhibits an impossibility of the Gibbard-Satterthwaite type. Moreover, this impossibility is inherited by all well-known superdomains of D-lambda. As most of the standard extension axioms induce superdomains of D-lambda while social choice correspondences are particular social choice hyperfunctions, we are able to generalize many impossibility results in the literature. (C) 2008 Elsevier Inc. All rights reserved.Öğe How to Elect a Representative Committee Using Approval Balloting(Springer-Verlag Berlin, 2006) Kilgour, D. Marc; Brams, Steven J.; Sanver, M. RemziApproval balloting is applied to the problem of electing a representative committee. We demonstrate several procedures for determining a committee based on approval ballots, paying particular attention to weighting methods that can reduce the influence of voters with extreme views. We show that a general class of voting systems based on approval ballots can be implemented through analysis of appropriate tables. A by-product of this procedure is a clarification of the complexity of these systems.Öğe Introduction to the Handbook on Approval Voting(Springer-Verlag Berlin, 2010) Laslier, Jean-Francois; Sanver, M. Remzi[Abstract Not Available]Öğe Is abstention an escape from Arrow's theorem?(Springer, 2007) Cengelci, Murat Ali; Sanver, M. RemziIn a society of variable size, Quesada (Soc Choice Welfare 25(1): 221-226, 2005) establishes the existence of Arrovian social welfare functions which are not dictatorial. We show that this escape from the Arrovian impossibility collapses when a very mild monotonicity condition is introduced.Öğe Metrizable preferences over preferences(Springer, 2020) Laffond, Gilbert; Laine, Jean; Sanver, M. RemziA hyper-preference is a weak order over all linear orders defined over a finite set A of alternatives. An extension rule associates with each linear order p over A a hyper-preference. The well-known Kemeny extension rule ranks all linear orders over A according to their Kemeny distance to p. More generally, an extension rule is metrizable iff it extends p to a hyper-preference consistent with a distance criterion. We characterize the class of metrizable extension rules by means of two properties, namely self-consistency and acyclicity across orders. Moreover, we provide a characterization of neutral and metrizable extension rules, based on a simpler formulation of acyclicity across orders. Furthermore, we establish the logical incompatibility between neutrality, metrizability and strictness. However, we show that these three conditions are pairwise logically compatible.Öğe A Minimax Procedure for Negotiating Multilateral Treaties(Springer-Verlag Berlin, 2007) Brams, Steven J.; Kilgour, D. Marc; Sanver, M. Remzi[Abstract Not Available]Öğe Monotonicity properties and their adaptation to irresolute social choice rules(Springer, 2012) Sanver, M. Remzi; Zwicker, William S.What is a monotonicity property? How should such a property be recast, so as to apply to voting rules that allow ties in the outcome? Our original interest was in the second question, as applied to six related properties for voting rules: monotonicity, participation, one-way monotonicity, half-way monotonicity, Maskin monotonicity, and strategy-proofness. This question has been considered for some of these properties: by Peleg and BarberA for monotonicity, by Moulin and P,rez et al, for participation, and by many authors for strategy-proofness. Our approach, however, is comparative; we examine the behavior of all six properties, under three general methods for handling ties: applying a set extension principle (in particular, Gardenfors' sure-thing principle), using a tie-breaking agenda to break ties, and rephrasing properties via the t-a-t approach, so that only two alternatives are considered at a time. In attempting to explain the patterns of similarities and differences we discovered, we found ourselves obliged to confront the issue of what it is, exactly, that identifies these properties as a class. We propose a distinction between two such classes: the tame monotonicity properties (which include participation, half-way monotonicity, and strategy proofness) and the strictly broader class of normal monotonicity properties (which include monotonicity and one-way monotonicity, but not Maskin monotonicity). We explain why the tie-breaking agenda, t-a-t, and Gardenfors methods are equivalent for tame monotonicities, and how, for properties that are normal but not tame, set-extension methods can fail to be equivalent to the other two (and may fail to make sense at all).Öğe Nash implementability of the plurality rule over restricted domains(Elsevier Science Sa, 2008) Sanver, M. RemziWe give a complete characterization of preference domains over which the plurality rule is Nash implementable. We show that the plurality rule fails Nash implementability on every domain except those which are monotonically trivial. (C) 2007 Elsevier B.V. All rights reserved.Öğe Nash implementation of the majority rule(Elsevier Science Sa, 2006) Sanver, M. RemziGiven a society confronting two alternatives, we show that the absolute majority rule is the minimal Nash implementable extension of the relative majority rule. (c) 2005 Elsevier B.V All rights reserved.
