Group strategy-proof social choice functions with binary ranges and arbitrary domains: characterization results

We define different concepts of group strategy-proofness for social choice functions. We discuss the connections between the defined concepts under different assumptions on their domains of definition. We characterize the social choice functions that satisfy each one of them and whose ranges consist of two alternatives, in terms of two types of basic properties. Finally, we obtain the functional form of all rules satisfying our strongest version of group strategy-proofness.     

The golden rule when preferences are time inconsistent

We investigate the classical Ramsey problem of economic growth when the planner uses non-constant discounting. It is well-known that this leads to time inconsistency, so that optimal strategies are no longer implementable. We then define equilibrium strategies to be such that unilateral deviations occurring during a small time interval are penalized. Non-equilibrium strategies are not implementable, so only equilibrium strategies should be considered by a rational planner. We show that there exists such strategies which are (a) smooth, and (b) lead to stationary growth, as in the classical Ramsey model. Finally, we prove an existence and multiplicity result: for logarithmic utility and quasi-exponential discount, there is an interval I such that, for every k in I, there is an equilibrium strategy converging to k. We conclude by giving an example where the planner is led to non-constant discount rates by considerations of intergenerational equity.     

Efficient experimental designs when most treatments are unreplicated

In early generation variety trials, large numbers of new breeders’ lines (varieties) may be compared, with each having little seed available. A so-called unreplicated trial has each new variety on just one plot at a site, but includes several replicated control varieties, making up around 10% and 20% of the trial. The aim of the trial is to choose some (usually around one third) good performing new varieties to go on for further testing, rather than precise estimation of their mean yields.Now that spatial analyses of data from field experiments are becoming more common, there is interest in an efficient layout of an experiment given a proposed spatial analysis and an efficiency criterion. Common optimal design criteria values depend on the usual C-matrix, which is very large, and hence it is time consuming to calculate its inverse. Since most varieties are unreplicated, the variety incidence matrix has a simple form, and some matrix manipulations can dramatically reduce the computation needed. However, there are many designs to compare, and numerical optimisation lacks insight into good design features. Some possible design criteria are discussed, and approximations to their values considered. These allow the features of efficient layouts under spatial dependence to be given and compared.     

Exact choice and fuzzy preferences

Agents often have to make exact choices on the basis of vague preferences. Therefore analysis of the way in which exact choices are induced by vague preferences is of considerable interest. In this paper we use the model of vague preferences as fuzzy orderings. One objective of this paper is conceptual in nature: we discuss several alternative notions of exact choice sets generated by a fuzzy preference ordering and corresponding notions of rationalizability of exact choices in terms of fuzzy preference orderings. The second objective of this paper is to explore conditions for rationalizability of exact choices in terms of a fuzzy preference ordering, under alternative definitions of such rationalizability.     

Up methods in the allocation of indivisibilities when preferences are single-peaked

We consider allocation problems with indivisible goods when agents’ preferences are single-peaked. We propose natural rules (called up methods) to solve such a class of problems and axiomatically characterize them. We also prove that these methods can be interpreted as extensions to the indivisible case of the so-called equal distance rule.      

A maximal domain for strategy-proof and no-vetoer rules in the multi-object choice model

Following “Barberà et al. (1991, Econometrica 59:595–609)”, we study rules (or social choice functions) through which agents select a subset from a set of objects. We investigate domains on which there exist nontrivial strategy-proof rules. We establish that the set of separable preferences is a maximal domain for the existence of rules satisfying strategy-proofness and no-vetoer.     

Rational choice based on vague preferences

This paper studies vague preferences. In contrast to the concept of fuzzy preferences, the more general notion of vague preferences does not entail the assumption that the different degrees of preference are completely ordered. It is shown that the more general concept of a vague preference order arises very naturally in the context of aggregating a set of (exact) weak orders. Furthermore, necessary and sufficient conditions for the rationalizability of an exact choice function by means of a vague preference order are given. It turns out that in the general case these conditions are weaker than in the case where the degrees of preference are completely ordered. Consequently, there exist choice functions which are rationalizable by a general vague preference order but which are not rationalizable by a fuzzy preference order, or more generally by any vague preference order which induces a complete ranking of the degrees of preference. Examples of such choice functions are provided.This is a revised version of a discussion paper which was written at the University of Karlsruhe. I am grateful to Georg Bol and an anonymous referee for valuable comments. The research has been made possible by a fellowship of the DFG (Deutsche Forschungsgemeinschaft) which is also gratefully acknowledged.     

On non-binary social choice

In a recent paper Grether and Plott (1982) have extended Arrow's General Possibility Theorem to the case where choice over small (in particular ‘two-element’) sets may not be possible. This obviously raises the question whether the counterparts of other existing impossibility results will go through in the same framework. This note settles the question for the counterpart of the well-known impossibility theorem of Gibbard. By weakening the collective rationality condition of Arrow we show that all the social choice functions will be ‘oligarchical’ in Gibbard's sense, in the Grether and Plott (1982) framework.     

Triple-consistent social choice and the majority rule

We define generalized (preference) domains \(\mathcal{D}\) as subsets of the hypercube {?1,1} ^D , where each of the D coordinates relates to a yes-no issue. Given a finite set of n individuals, a profile assigns each individual to an element of \(\mathcal{D}\) . We prove that, for any domain \(\mathcal{D}\) , the outcome of issue-wise majority voting φ _m belongs to \(\mathcal{D}\) at any profile where φ _m is well-defined if and only if this is true when φ _m is applied to any profile involving only 3 elements of \(\mathcal{D}\) . We call this property triple-consistency. We characterize the class of anonymous issue-wise voting rules that are triple-consistent, and give several interpretations of the result, each being related to a specific collective choice problem.     

Multi-attribute decision-making in individual and social choice

This paper provides an analysis of individual and social decision criteria for alternatives that are composed of several attributes. We derive additive and multiplicative criteria for individual decision-making with new axioms and apply these criteria to obtain new justifications of known social choice rules with a bargaining interpretation, namely the generalized utilitarian and Nash social choice functions. Unlike most axiomatizations of bargaining solutions, our approach is, to a large extent, based on the multi-attribute structure of the underlying alternatives and the resulting individual decision criteria instead of axioms that impose restrictions on the choice function directly.     

Restricted preferences and strategyproofness of singlevalued social decision functions

The paper examines the possibility of imposing reasonable restrictions on sincere preferences of individuals to rule out strategic misrevelation of preferences. In this connection, Zeckhauser had originally conjectured that singlepeakedness of sincere individual preferences would be sufficient for strategyproofness. The main result of the paper is to show that singlecavedness, and not singlepeakedness, rules out strategic misrevelation of preferences by groups of individuals.     

On a compromise social choice correspondence

This paper analyzes the compromise social choice correspondence derived from the τ-value of digraph games. Monotonicity of this correspondence is shown. A connection between several properties of social choice correspondences based on game theoretical solutions and game theoretical properties of the underlying solutions is given. Applications to several game theoretic solutions are provided.     

Multi-utilitarianism in two-agent quasilinear social choice

We introduce a new class of rules for resolving quasilinear social choice problems. These rules extend those of Green [9]. We call such rules multi-utilitarian rules. Each multi-utilitarian rule is associated with a probability measure over the set of weighted utilitarian rules, and is derived as the expectation of this probability. These rules are characterized by the axioms efficiency, translation invariance, transfer monotonicity, continuity, and additivity. By adding recursive invariance, we obtain a class of asymmetric rules generalizing those Green characterizes. A multi-utilitarian rule satisfying strict monotonicity has an associated probability measure with full support.I would like to thank Youngsub Chun, Federico Echenique, Jerry Green, Biung-Ghi Ju, William Thomson, and Walter Trockel for comments and discussions. Two anonymous referees also provided comments that proved very useful. All errors are my own.     

Informational requirements of social choice rules

The required amount of information to make a social choice is the cost of information processing, and it is a practically important feature of social choice rules. We introduce informational aspects into the analysis of social choice rules and prove that (i) if an anonymous, neutral, and monotonic social choice rule operates on minimal informational requirements, then it is a supercorrespondence of either the plurality rule or the antiplurality rule, and (ii) if the social choice rule is furthermore Pareto efficient, then it is a supercorrespondence of the plurality rule.     

Constitutional implementation of social choice correspondences

A game form constitutionally implements a social choice correspondence if it implements it in Nash equilibrium and, moreover, the associated effectivity functions coincide. This paper presents necessary and sufficient conditions for a unanimous social choice correspondence to be constitutionally implementable, and sufficient and almost necessary conditions for an arbitrary (but surjective) social choice correspondence to be constitutionally implementable. It is shown that the results apply to interesting classes of scoring and veto social choice correspondences.     

Equity,efficiency and rights in social choice

The impossibility of a Paretian liberal presented by Sen shows the incompatibility of the Pareto principle with a mild claim of libertarian rights when they are required of the collective choice rule with unrestricted domain. In view of the profound implications of this paradox, it is no wonder that there are many serious attempts in the literature to seek for a general resolution thereof. In this paper, we try to explore an avenue which has been left relatively less cultivated in the attempts to try to find a way out of this paradox, the essential idea thereof being to restrict the ‘legitimate’ exercise of the liberatarian rights by the claims of justice or equity. It will be shown that the gist of the successful resolution of the Pareto libertarian paradox along this line lies in the impartiality of the principle of justice held by the individuals and the prevalence of the sympathetic acceptance of each other's subjective preferences.     

Correlation when data are missing

Variable correlation is important for many operations research models. Manyinventory, revenue management, and queuing models presume uncorrelated demandbetween products, market segments, or time periods. The specific model applied,or the resulting policies of a model, can differ drastically depending onvariable correlation. Having missing data are a common problem for the realworld application of operations research models. This work is at the junction ofthe two topics of correlation and missing data. We propose a test ofindependence between two variables when data are missing. The typical method fordetermining correlation with missing data ignores all data pairs in which onepoint is missing. The test presented here incorporates all data. The test can beapplied when both variables are continuous, when both are discrete, or when onevariable is discrete and the other is continuous. The test makes no assumptionsabout the distribution of the two variables, and thus it can be used to extendapplication of non-parametric rank tests, such as Spearman's rankcorrelation, to the case where data are missing. An example is shown wherefailure to incorporate the incomplete data yields incorrect policies.     

The categorical approach to social choice theory

A number of different problems in social choice theory are given a common treatment in the framework of category theory. A social choice function is a map μ from a set Hom(A, PX) of profiles - in applications functions from a set A of agents to the set PX of linear orders on a set X of alternatives - to a set GPX the nature of which depends on the application. The main theorem established is applied to social welfare functions and strategy-proof voting schemes.