An alternative direct proof of Gibbard’s random dictatorship theorem

We present an alternative proof of the Gibbards random dictatorship theorem with ex post Pareto optimality. Gibbard(1977) showed that when the number of alternatives is finite and larger than two, and individual preferences are linear (strict), a strategy-proof decision scheme (a probabilistic analogue of a social choice function or a voting rule) is a convex combination of decision schemes which are, in his terms, either unilateral or duple. As a corollary of this theorem (credited to H. Sonnenschein) he showed that a decision scheme which is strategy-proof and satisfies ex post Pareto optimality is randomly dictatorial. We call this corollary the Gibbards random dictatorship theorem. We present a proof of this theorem which is direct and follows closely the original Gibbards approach. Focusing attention to the case with ex post Pareto optimality our proof is more simple and intuitive than the original Gibbards proof.Received: 15 October 2001, Accepted: 23 May 2003, JEL Classification: D71, D72Yasuhito Tanaka: The author is grateful to an anonymous referee and the Associate editor of this journal for very helpful comments and suggestions. And this research has been supported by a grant from the Zengin Foundation for Studies on Economics and Finance in Japan.     

A mechanism design approach to allocating central government funds among regional development agencies

To allocate central government funds among regional development agencies, we look for mechanisms that satisfy three important criteria: efficiency, (individual and coalitional) strategy proofness (a.k.a. dominant strategy incentive compatibility), and fairness. We show that only a uniform mechanism satisfies all three. We also show that all efficient and strategy proof mechanisms must function by assigning budget sets to the agencies and letting them freely choose their optimal bundle. In choosing these budget sets, the agencies’ private information has to be taken into account in a particular way. The only way to additionally satisfy a weak fairness requirement (regions with identical preferences should be treated equally) is to assign all agencies the same budget set, as does the uniform mechanism. Finally and maybe more importantly, we show that the central government should not impose constraints on how much to fund an activity (e.g. by reserving some funds only for a particular activity): otherwise, there are no efficient, strategy proof and fair mechanisms, no matter how small these constraints are.     

The structure of strategy-proof random social choice functions over product domains and lexicographically separable preferences

We characterize the class of dominant-strategy incentive-compatible (or strategy-proof) random social choice functions in the standard multi-dimensional voting model where voter preferences over the various dimensions (or components) are lexicographically separable. We show that these social choice functions (which we call generalized random dictatorships) are induced by probability distributions on voter sequences of length equal to the number of components. They induce a fixed probability distribution on the product set of voter peaks. The marginal probability distribution over every component is a random dictatorship. Our results generalize the classic random dictatorship result in Gibbard (1977) and the decomposability results for strategy-proof deterministic social choice functions for multi-dimensional models with separable preferences obtained in LeBreton and Sen (1999).     

Intransitive social indifference and the Arrow dilemma

This paper deals with a proposal by Frederic Schick for resolving Arrow’s dilemma of social choice. Schick challenges Arrow’s assumption that rational social indifference is transitive. It turns out, however, that even if we drop this assumption, we still face a dilemma as embarrassing as Arrow’s. Any constitution which satisfies the remaining conditions is a liberum veto oligarchy. This means a unique set of individuals carries any issue on which it is unanimous, and engenders social indifference on any issue which divides it. A formal statement and proof of this theorem follows an informal presentation of the result.     

On the equivalence of the Arrow impossibility theorem and the Brouwer fixed point theorem when individual preferences are weak orders

We will show that in the case where there are two individuals and three alternatives (or under the assumption of the free-triple property), and individual preferences are weak orders (which may include indifference relations), the Arrow impossibility theorem [Arrow, K.J., 1963. Social Choice and Individual Values, second ed. Yale University Press] that there exists no binary social choice rule which satisfies the conditions of transitivity, Pareto principle, independence of irrelevant alternatives, and non-existence of dictator is equivalent to the Brouwer fixed point theorem on a 2-dimensional ball (circle). Our study is an application of ideas by Chichilnisky [Chichilnisky, G., 1979. On fixed points and social choice paradoxes. Economics Letters 3, 347–351] to a discrete social choice problem, and also it is in line with the work by Baryshnikov [Baryshnikov, Y., 1993. Unifying impossibility theorems: a topological approach. Advances in Applied Mathematics 14, 404–415].     

A model of stochastic choice from lists

We study stochastic choice from lists. All lists present the same set of alternatives albeit in different orders. Faced with a list, the decision maker makes her choice in two stages. In the first stage she searches through the list till she sees $k$ alternatives. In the second stage she chooses from the alternatives she has seen. Both $k$ and the choice rule governing her second stage behavior are random. We show that the underlying primitives of our model are revealed by the decision maker’s choice frequencies from lists. We characterize the model and two of its special cases. In the first special case the decision maker deterministically chooses the best observed alternative according to a given preference. In the second, the decision maker maximizes random preferences.     

The topological equivalence of the pareto condition and the existence of a dictator

The paper studies two standard properties of rules for aggregating individual into social preferences: non-dictatorship and the Pareto condition. Together with the condition of independence of irrelevant alternatives, these are the three basic axioms of Arrow's social choice paradox.We prove the topological equivalence between the Pareto condition and the existence of a dictator for continuous rules. The axiom of independence of irrelevant alternatives is not required.The results use a topological framework for aggregation introduced in Chichilnisky (1980), but under different conditions. In Chichilnisky (1980) rules are anonymous and respect unanimity. Since anonymity is strictly stronger than the condition of non-dictatorship, while respect of unanimity is strictly weaker than the Pareto condition, the two sets of conditions are not comparable.     

Relaxing IIA and the effect on individual power

We allow departures from IIA in Arrow’s framework. Our measure of the extent of a departure is the amount of information needed to socially order a pair of alternatives. We also propose a measure of the scope of an individual’s power. The scope of at least one individual’s power increases in step with a reduction in the amount of information that has to be gathered to socially order two alternatives. This result is also established for correspondences, which select a subset of the feasible set as a function of individual preferences.     

On the computability of quasi-transitive binary social choice rules in an infinite society and the halting problem

This paper investigates the computability problem of the existence of a vetoer and an oligarchy for quasi-transitive binary social choice rules (Mas-Colell and Sonnenschein in Rev Econ Stud 39:185–192, 1972) in a society with an infinite number of individuals (infinite society) according to the computable calculus (or computable analysis) by Aberth (Computable analysis, McGraw-Hill, New York, 1980; Computable calculus, Academic Press, Dublin, 2001). We will show the following results. The problem whether a quasi-transitive binary social choice rule which satisfies Pareto principle and independence of irrelevant alternatives (IIA) has a vetoer or has no vetoer in an infinite society is a nonsolvable problem, that is, there exists no ideal computer program for a quasi-transitive binary social choice rule which satisfies Pareto principle and IIA that decides whether it has a vetoer or has no vetoer. And it is equivalent to nonsolvability of the halting problem. We also show that if for any quasi-transitive binary social choice rule there exists an oligarchy in an infinite society, whether it is finite or infinite is a nonsolvable problem. A vetoer is an individual such that if he strictly prefers an alternative to another alternative, then the society prefers the former to the latter or is indifferent between them regardless of the preferences of other individuals, and an oligarchy is the minimal set of individuals which has dictatorial power and its each member is a vetoer. It will be shown that an oligarchy is a set of vetoers if it exists. This research was partially supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (C), 20530165, and the Grant-in-Aid from the Zengin Foundation for Studies on Economics and Finance in Japan.     

Erratum to “Walras and dividends equilibrium with possibly satiated consumers”

The main contribution of the paper is to provide a weaker nonsatiation assumption than the one commonly used in the literature to ensure the existence of competitive equilibrium. Our assumption allows for satiation points in the set of individually feasible consumptions, provided that the consumer has satiation points available to him outside this set. As a result, we show the concept of equilibrium with dividends (see Aumann, R.J., Drèze, J.H., 1986. Values of markets with satiation or fixed prices. Econometrica 54, 1271–1318; Mas-Collel, A., 1992. Equilibrium theory with possibly satiated preferences. In: Majumdar, M. (Ed.), Equilibrium and Dynamics: Proceedings of the Essays in Honour of David Gale. MacMillan, London, pp. 201–213) is pertinent only when the set of satiation points is included in the set of individually feasible consumptions. Our economic motivation stems from the fact that in decentralized markets, increasing the incomes of consumers through dividends, if it is possible, is costly since it involves the intervention of a social planner. Then, we show, in particular, how in securities markets our weak nonsatiation assumption is satisfied by Werner’s (1987) assumption.     

Increasing sales by introducing non‐salable items

Rationality implies that adding ‘irrelevant’ and, in particular, inferior alternatives to the opportunity set cannot increase the choice probability of some other alternative. In this study, we propose a novel approach that can rationalize an intended addition of such alternatives because it strictly increases the choice probability of some existing alternative. The driving force behind the existence and extent of such an increase is the random nature of individual preferences, that implies intransitivity, and the random nature of the applied choice procedures. We study the case of a firm interested in increasing the sales of some of its existing products by introducing a new and inferior (non‐salable) product. Our main results focus on the feasibility and potential advantage of a successful such strategy. We first establish necessary and sufficient conditions for an increase in the sale probability and then derive the maximal possible absolute and relative increase in this probability, when the firm has extremely limited information on the characteristics of the consumers. We then derive analogous results, assuming that the existing line of products consists of just two items and that the firm has accurate information on the consumers' stochastic preferences over the existing products. These later results are illustrated using some experimental evidence. The applicability of the approach is finally briefly discussed in the context of branding policy. Copyright © 2006 John Wiley & Sons, Ltd.     

Weighted scoring rules,the impartial culture condition,and homogeneity

The study considers the significance of weight selection for weighted scoring rules on three alternatives. Most research previously done in this area has been based on the assumption of the impartial culture condition. Intuition suggests that if preferences of individuals in a large group are at all distant or different from the impartial culture condition, then the weights selected for a weighted scoring rule become unimportant. It would seem likely in such a situation that one of the alternatives should be a clear front runner and win under almost any weighted scoring rule. A measure of social homogeneity is used in the study to represent the distance between a given set of individuals' preferences and the impartial culture condition. Based on computer simulation analysis, the results indicate that specific weight selection definitely becomes less important as the level of social homogeneity increases. However, the specific weight selection is still found to be of importance for situations with the greatest homogeneity that represent preferences the farthest distance from the condition of impartial culture.     

Preference aggregation and atoms in measures

This paper examines the aggregation of preferences with a finitely additive measure space of agents. We consider three types of non-dictatorship axioms: non-dictatorship, coalitional non-dictatorship, and atomic non-dictatorship. First, we show that the existence of an atom is a necessary and sufficient condition for the existence of a social welfare function that satisfies weak Pareto, independence of irrelevant alternatives, and coalitional non-dictatorship. Second, we simultaneously impose non-dictatorship and coalitional non-dictatorship, and specify a necessary and sufficient condition for the finitely additive measure that guarantees the compatibility among the axioms. Third, we impose all non-dictatorship axioms and show that the corresponding measure is extremely restricted.     

Arrovian social choice with psychological thresholds

This paper studies Arrovian preference aggregation rules–the rules satisfying weak Pareto and Arrow’s independence of irrelevant alternatives (IIA)–when individual preferences are nontransitive due to the existence of psychological thresholds — a problem of perceptible difference. A new domain replaces the universal domain, and rationality requirements of social preferences, i.e., transitivity, quasi-transitivity, and acyclicity with indifference transitivity, are converted into the corresponding versions respectively. We show that the Arrovian impossibilities, i.e., dictator, oligarchy, and vetoer theorems, still survive in this setting.     

A topological approach to Wilson’s impossibility theorem

We will present a topological approach to Wilson’s impossibility theorem [Wilson, R.B., 1972. Social choice theory without the Pareto principle. Journal of Economic Theory 5, 478–486] that there exists no non-null binary social choice rule which satisfies transitivity, independence of irrelevant alternatives, non-imposition and has no dictator nor inverse dictator. Our research is in line with the studies of topological approaches to discrete social choice problems initiated by [Baryshnikov, Y., 1993. Unifying impossibility theorems: a topological approach. Advances in Applied Mathematics 14, 404–415]. This paper extends the result about the Arrow impossibility theorem shown in [Tanaka, Y., 2006. A topological approach to the Arrow impossibility theorem when individual preferences are weak orders. Applied Mathematics and Computation 174, 961–981] to Wilson’s theorem.     

An equity characterization of second price auctions when preferences may not be quasilinear

In a single item auction model that allows non-quasilinear preferences, we show that an auction rule satisfies weak envy-freeness for equals, strategy-proofness, and nonimposition if and only if it is a (generalized) second price auction. This characterization is established on a wide class of preference domains, including the quasilinear domain, a positive income effect domain, and a negative income effect domain.     

Fuzzy multi-linguistic preferences model of service innovations at wholesale service delivery

In group decision making, most researches often assume the linguistic ways with personal preferences have been given and ignore the linguistic evaluated formats involving their knowledge and experience. In practice, people contributing to the judgment tend generally to give ratings about their personal preferences depending on their background. Thus, problems in multiple linguistic preferences go undetected, resulting in the evaluation process not satisfying with decisions’ expectations. In this study, we provide a fuzzy multiple preference integrated model with two stages to better reduce the bias for group decision makings. The first stage focuses on making the information unify on the alternatives according to the individual linguistic preferences, then we compute collective performance values and solve the problems lacking on the integration of respective fuzzy choice subsets. The second stage, we choose the alternatives of retailing service innovations according to the collective performance values by stage one. The goal of the decision process is to reach the subjective fuzzy cognitions in terms of the preference values of all the decision makers. Finally, the survey data of the chain wholesale using multiple preference formats in service innovations determination is verified.     

On rankings and top choices in random utility models with dependent utilities

Different aggregate preference orders based on rankings and top choices have been defined in the literature to describe preferences among items in a fixed set of alternatives. A useful tool in this framework is constituted by random utility models, where the utility of each alternative, or object, is represented by a random variable, indexed by the object, which, for example, can capture the variability of preferences over a population. Applications are derived in diverse research fields, including computer science, management science and reliability. Recently, some stochastic ordering conditions have been provided for comparing alternatives by means of some aggregate preference orders in the case of independent random utility variables by Joe (Math Soc Sci 43:391–404, 2002). In this paper we provide new conditions, based on some joint stochastic orderings, for aggregate preference orders among the alternatives in the case of dependent random utilities. We also provide some examples of application in different research fields.      

Satiation and existence of competitive equilibrium

In this paper, we introduce a new assumption concerning the (non)satiation property of preferences and establish the existence of a competitive equilibrium under it. The assumption is weaker than the standard nonsatiation assumption and “weak nonsatiation” introduced by Allouch and Le Van (2008). In particular, it allows preferences to be satiated only inside the set of individually rational feasible consumptions, while the two nonsatiation assumptions do not. It is also worth noting that just like the two nonsatiation assumptions, our new assumption depends solely on the characteristics of consumers.     

Unanimity,anonymity, and infinite population

This paper is concerned with the implications of unanimity and anonymity for the Arrovian social choice theory when population is infinite. Contrary to the finite population case, various unanimity and anonymity axioms can be formulated. We show a tension between unanimity and anonymity by providing possibility and impossibility results. We also examine the case in which social preferences are allowed to be quasi-transitive.