The premiss-based approach to judgment aggregation

In the framework of judgment aggregation, we assume that some formulas of the agenda are singled out as premisses, and that both Independence (formula-wise aggregation) and Unanimity Preservation hold for them. Whether premiss-based aggregation thus defined is compatible with conclusion-based aggregation, as defined by Unanimity Preservation on the non-premisses, depends on how the premisses are logically connected, both among themselves and with other formulas. We state necessary and sufficient conditions under which the combination of both approaches leads to dictatorship (resp. oligarchy), either just on the premisses or on the whole agenda. Our analysis is inspired by the doctrinal paradox of legal theory and is arguably relevant to this field as well as political science and political economy. When the set of premisses coincides with the whole agenda, a limiting case of our assumptions, we obtain several existing results in judgment aggregation theory.     

Judgment aggregation: (im)possibility theorems

The aggregation of individual judgments over interrelated propositions is a newly arising field of social choice theory. I introduce several independence conditions on judgment aggregation rules, each of which protects against a specific type of manipulation by agenda setters or voters. I derive impossibility theorems whereby these independence conditions are incompatible with certain minimal requirements. Unlike earlier impossibility results, the main result here holds for any (non-trivial) agenda. However, independence conditions arguably undermine the logical structure of judgment aggregation. I therefore suggest restricting independence to “premises”, which leads to a generalised premise-based procedure. This procedure is proven to be possible if the premises are logically independent.     

Majority voting on restricted domains

In judgment aggregation, unlike preference aggregation, not much is known about domain restrictions that guarantee consistent majority outcomes. We introduce several conditions on individual judgments sufficient for consistent majority judgments. Some are based on global orders of propositions or individuals, others on local orders, still others not on orders at all. Some generalize classic social-choice-theoretic domain conditions, others have no counterpart. Our most general condition generalizes Sen's triplewise value-restriction, itself the most general classic condition. We also prove a new characterization theorem: for a large class of domains, if there exists any aggregation function satisfying some democratic conditions, then majority voting is the unique such function. Taken together, our results support the robustness of majority rule.     

The possibility of judgment aggregation on agendas with subjunctive implications

The new field of judgment aggregation aims to find collective judgments on logically interconnected propositions. Recent impossibility results establish limitations on the possibility to vote independently on the propositions. I show that, fortunately, the impossibility results do not apply to a wide class of realistic agendas once propositions like “if a then b” are adequately modelled, namely as subjunctive implications rather than material implications. For these agendas, consistent and complete collective judgments can be reached through appropriate quota rules (which decide propositions using acceptance thresholds). I characterise the class of these quota rules. I also prove an abstract result that characterises consistent aggregation for arbitrary agendas in a general logic.     

Judgment aggregation in search for the truth

We analyze the problem of aggregating judgments over multiple issues from the perspective of whether aggregate judgments manage to efficiently use all voters' private information. While new in judgment aggregation theory, this perspective is familiar in a different body of literature about voting between two alternatives where voters' disagreements stem from conflicts of information rather than of interest. Combining the two bodies of literature, we consider a simple judgment aggregation problem and model the private information underlying voters' judgments. Assuming that voters share a preference for true collective judgments, we analyze the resulting strategic incentives and determine which voting rules efficiently use all private information. We find that in certain, but not all cases a quota rule should be used, which decides on each issue according to whether the proportion of ‘yes’ votes exceeds a particular quota.     

Factoring out the impossibility of logical aggregation

According to a theorem recently proved in the theory of logical aggregation, any nonconstant social judgment function that satisfies independence of irrelevant alternatives (IIA) is dictatorial. We show that the strong and not very plausible IIA condition can be replaced with a minimal independence assumption plus a Pareto-like condition. This new version of the impossibility theorem likens it to Arrow's and arguably enhances its paradoxical value.     

Aggregation of binary evaluations

We study a general aggregation problem in which a society has to determine its position (yes/no) on each of several issues, based on the positions of the members of the society on those issues. There is a prescribed set of feasible evaluations, i.e., permissible combinations of positions on the issues. This framework for the theory of aggregation was introduced by Wilson and further developed by Rubinstein and Fishburn. Among other things, it admits the modeling of preference aggregation (where the issues are pairwise comparisons and feasibility reflects rationality), and of judgment aggregation (where the issues are propositions and feasibility reflects logical consistency). We characterize those sets of feasible evaluations for which the natural analogue of Arrow's impossibility theorem holds true in this framework.     

科学、价值与判断在环境影响评估架构中之整合

公共政策研拟，尤其是环境影响评估，不仅牵涉技术性科学层面，同时涵盖社会性价值评估与政策性决策判断。旨在探讨如何将科学、价值与判断等因素合理融合于环境影响评估作业过程中，并据此研拟一环境影响评估架构，作为中国台湾地区环保部门开发案审核依据之参考。本文所研拟之环境影响评估架构的理论基础包括社会选择理论、社会判断理论及多属性评估方法。通过社会选择理论分析环境政策制定的机制；通过社会判断理论解释科学与价值如何整合于政策制定及其可行性中；而通过多属性评估方法建立开发案评选的集体决策技术。以山坡地开发为例说明此架构在实践中的应用。     

Justifiable group choice

We study the judgment aggregation problem from the perspective of justifying a particular collective decision by a corresponding aggregation on the criteria. In particular, we characterize the logical relations between the decision and the criteria that enable justification of a majority decision through a proposition-wise aggregation rule with no veto power on the criteria. While the well-studied “doctrinal paradox” provides a negative example in which no such justification exists, we show that genuine possibility results emerge if there is a gap between the necessary and the sufficient conditions for the decision. This happens, for instance, if there is only a partial consensus about the appropriate criteria for the decision, if only a subset of these criteria can be elicited, or if the judgment on criteria is based on probabilistic acceptance thresholds.     

Is diversity in Delphi panelist groups useful? Evidence from a French forecasting exercise on the future of nuclear energy

This paper further enhances the analytical power of Delphi methodology by identifying the advantages, disadvantages and challenges presented by increasing diversity among panel groups. Using Delphi survey data on the future of nuclear energy in France, we analyze the origins of the variety of judgments within and between two panels: one of experts and one of laypeople. We investigate the determinants of the stability of those opinions both in one given round and over several rounds of opinion-formation. We reach an apparently paradoxical conclusion: that non-expert judgment is less stable, but not necessarily less accurate, than that of experts, judgments on the part of experts sometimes being clouded by self-interest. Apart from highlighting some factors underlying the controversy over nuclear power, our paper calls for greater participatory democracy in Delphi panels, but also demonstrates the limits of such an extension.     

Towards a framework to understand purpose in Futures Studies: The role of Vickers' Appreciative System

There have been comments recently about the efficacy of Futures Studies (and scenario planning) projects, relating to confusion on knowledge aggregation and methodology, which can be summarised in the question: “how to determine the purpose of such projects”. The lack of a purpose framework makes it difficult for ‘clients’ initiating such projects to determine if outcomes meet their original expectations. This paper proposes a framework to help understand the nature, objective and purpose of Futures Studies (and scenario planning) projects, which we will argue helps to overcome these concerns. The proposed framework is based on Vickers' definition of an Appreciative System, highlighting how decision making involves three areas of judgment — reality judgment, value judgment, and instrumental judgment. It will be argued that decision-makers and policymakers call for Futures Studies projects when they become aware of an organizational deficiency in one or more of these areas.Each element, alone or in combination, could form the basis of a purpose definition for a Futures Studies project, and, therefore, needs to be considered to ensure that the project meets client expectations and is experienced as purposeful and rewarding. The paper elaborates on each of the three elements, and then discusses their integrated nature. This is followed by a discussion of the implications of Appreciative System theory for three key players in the decision making process, the organizational leadership, the professionals and the organization at large involved in the practice of Futures Studies (and scenario planning) projects.     

Understanding modes of civil case disposition: Evidence from Slovenian courts

We contribute to the scant empirical literature on the functioning of courts in the post-socialist world by analyzing civil case disposition in Slovenia. We first characterize basic empirical patterns in modes of civil case disposition in Slovenian local courts. We then examine court-level determinants of the incidence of in-court settlements versus trial-based judgments. Consistent with the theory that both judges and disputing parties take into account their respective private benefits and costs when choosing their preferred mode of case disposition, we find evidence that the incidence of in-court settlements versus trial-based judgments increases with the number of all case filings per judge. Thus, court resources and demand for court services influence not only total court output, as previously established in the literature, but also how cases are disposed of.     

Developing business ethics theory and integrating economic analysis into business ethics teaching – a conceptualization based on externalities and diminishing marginal utility

Contrary to understandings that treat ethical considerations and economic thinking as separate if not antagonistic issues, we advocate a holistic view that links business ethics to consequentialist economic concepts and their concern about how scarce means should be used for the attainment of (given) ends. We believe that business ethics students will profit from a development of business ethics theory that facilitates an outcome-based evaluation of business strategies anchored in the economic concepts of externalities, game theory, equilibria, efficiency, transaction costs, and diminishing marginal utility. We outline how moral judgments about (socially irresponsible) business behaviors, which often lack theoretical grounding and self-critical examination, can be made both more consistent and transparent through a systematic application of these theoretical concepts. We furthermore point out that, in this evaluative exercise, business ethics analysts should make all assumptions explicit to meet their task of facilitating informed public debates and informed moral choices.     

Arrovian aggregation in economic environments: how much should we know about indifference surfaces?

Arrow's celebrated theorem of social choice shows that the aggregation of individual preferences into a social ordering cannot make the ranking of any pair of alternatives depend only on individual preferences over that pair, unless the fundamental weak Pareto and non-dictatorship principles are violated. In the standard model of division of commodities, we investigate how much information about indifference surfaces is needed to construct social ordering functions satisfying the weak Pareto principle and anonymity. We show that local information such as marginal rates of substitution or the shapes “within the Edgeworth box” is not enough, and knowledge of substantially non-local information is necessary.     

Weak measurability and characterizations of risk

Summary. In the context of a continuum of random variables, arising, for example, as rates of return in financial markets with a continuum of assets, or as individual responses in games with a continuum of players, an important economic issue is to show how idiosyncratic risk can be removed through some device of aggregation or diversification when such risk is explicitly introduced into the model. In this paper, we use recent work of Al-Najjar [1] as a general backdrop to provide a review of the basic issues involved when the continuum is formulated as the Lebesgue interval. We present two examples to argue that the fundamental problem of the non-measurability of sample functions, originally identified by Doob, and further elaborated by Feldman, Gilles and Judd in the economic literature, simply cannot be bypassed by reinterpretations of standard results. We also provide an equivalence result in the spirit of Al-Najjar's efforts; but argue that this elementary result does not go beyond the standard law of large numbers for a sequence of real-valued iid random variables, and as such, is incapable of yielding anything of substantive economic interest beyond this law. Received: April 23, 1998; revised version: April 28, 1998     

The analysis of expert judgment

Expert judgment is a necessary component of technology assessment. But current methods for attempting to integrate expert judgment with social value judgments in the formation of public policy are inappropriate and ineffective. This article advocates the scientific analysis of experts' judgments. Such analysis produces quantitative, pictorial models of expert judgment, thereby providing an explicit and retraceable procedure for a) documenting and comparing reasons for differences in expert judgment, b) helping experts to resolve such differences, and c) conveying information to decision makers in a clear and useful fashion. The proposed approach provides an alternative to the ineffective method of public hearings and recently proposed adversarial approaches such as the “science court.” Two studies are described to illustrate this approach.     

Viewpoint: Decision-making in committees

Abstract .  This article reviews recent developments in the theory of committee decision-making. A committee consists of self-interested members who make a public decision by aggregating imperfect information dispersed among them according to a pre-specified decision rule. We focus on costly information acquisition, strategic information aggregation, and rules and processes that enhance the quality of the committee decision. Seeming inefficiencies of the committee decision-making process such as over-cautiousness, voting, and delay emerge as partial remedies to these incentive problems.     

Symposium onMarket development and inequality in China1

After three decades of market development, the problem in China is no longer how to achieve growth but how to manage its consequences and how to sustain it. One of the most important consequences is the growing inequality – between skilled and unskilled workers, between the genders, between rural and urban areas, and between inland and coastal regions. The papers in this symposium shed light on the important issue of inequality during rapid market development in China. Analysis based on ground level empirical studies can help us to understand better the sources of the rising inequality and to illuminate the nature of the future challenges.     

Contemporary issues in empirical public finance

This paper provides a brief overview to how the use of game theory and its derivative theories of information and incentives in public finance have expanded economists' methodological toolkit for predicting how procedural aspects influence strategies of participants as well as their overall performance. Moreover given that evaluation of public policy options, where policy failures can and do occur due to either inadequate incentive structure or the presence of constitutional and behavioural constraints, the objective of the essays in this symposium is to indicate the richness and diversity of empirical approaches that have been used to shed quantitative light on applied public finance issues. First version received: May 1999/final version received: June 1999     

Testable implications of transferable utility

Although the Transferable Utility (TU) assumption is widely used in micro theory, little is known about its testable consequences, and in particular how one can, from the observation of a group's demand, test whether the TU assumption is satisfied within this group. We derive a set of necessary and sufficient conditions on demand that characterize the TU context. The conditions are of two types. First, TU requires the group to behave as a single decision maker. Secondly, within the unitary setting, the representative utility generated by a TU framework must be of the Generalized Quasi-Linear (GQL) form. We derive testable properties of the demand function that fully characterize GQL utilities. These additional restrictions only involve specific prices - namely, those of the goods that are publicly consumed within the group.