Explore the vast range of titles available.

From a formal point of view, a composite indicator is an aggregate of all dimensions, objectives, individual indicators and variables used for its construction. This implies that what defines a composite indicator is the set of properties underlying its mathematical aggregation convention. In this article, I try to revise the theoretical debate on aggregation rules by looking at contributions from both voting theory and multi-criteria decision analysis. This cross-fertilization helps in clarifying many ambiguous issues still present in the literature and allows discussing the key assumptions that may change the evaluation of an aggregation rule easily, when a composite indicator has to be constructed.

The year 2012 was the 30th anniversary of William H. Riker's modern classic Liberalism against populism (1982) and is marked by the present special issue. In this introduction, we seek to identify some core elements and evaluate the current status of the Rikerian research program and its empirical applications. Special attention is given to three phenomena and their possible empirical manifestations: The instability of social choice in the form of (1) the possibility of majority cycles, (2) the non-robustness of social choices given alternative voting methods, and (3) the possibility of various forms of manipulation of the decisions (heresthetics). These topics are then connected to the contributions to the current special issue.

Behavioural social choice has been proposed as a social choice parallel to seminal developments in other decision sciences, such as behavioural decision theory, behavioural economics, behavioural finance and behavioural game theory. Behavioural paradigms compare how rational actors should make certain types of decisions with how real decision makers behave empirically. We highlight that important theoretical predictions in social choice theory change dramatically under even minute violations of standard assumptions. Empirical data violate those critical assumptions. We argue that the nature of preference distributions in electorates is ultimately an empirical question, which social choice theory has often neglected. We also emphasize important insights for research on decision making by individuals. When researchers aggregate individual choice behaviour in laboratory experiments to report summary statistics, they are implicitly applying social choice rules. Thus, they should be aware of the potential for aggregation paradoxes. We hypothesize that such problems may substantially mar the conclusions of a number of (sometimes seminal) papers in behavioural decision research.

In a Borda count, BC, M. de Borda suggested the last preference cast should receive 1 point, the voter's penultimate ranking should get 2 points, and so on. Today, however, points are often awarded to (first, second,..., last) preferences cast as per(n,n−1, ..., 1) or more frequently, (n−1, n−2,..., 0). If partial voting¹ is allowed, and if a first preference is to be given n or n − 1 points regardless of how many preferences the voter casts, he/she will be incentivised to rank only one option/candidate. If everyone acts in this way, the BC metamorphoses into a plurality vote... which de Borda criticized at length. If all the voters submit full ballots, the outcome—social choice or ranking—will be the same under any of the above three counting procedures. In the event of one or more persons submitting a partial vote, however, outcomes may vary considerably. This preliminary paper suggests research should consider partial voting. The author examines the consequences of the various rules so far advocated and then purports that M. de Borda, in using his formula, was perhaps more astute than the science has hitherto recognised.

This paper analyzes the properties of runoff electoral systems when voters are strategic. A model of three-candidate runoff elections is presented, and two new features are included: the risk of upset victory in the second round is endogenous, and many types of runoff systems are considered. Three main results emerge. First, runoff elections produce equilibria in which only two candidates receive a positive fraction of the votes. Second, a sincere voting equilibrium does not always exist. Finally, runoff systems with a threshold below 50 percent produce an Ortega effect that may lead to the systematic victory of the Condorcet loser.

We study collective decisions by time-discounting individuals choosing a common consumption stream. We show that with any heterogeneity in time preferences, every Pareto efficient and non-dictatorial method of aggregating utility functions must be time-inconsistent We also show that decisions made via non-dictatorial voting methods are intransitive.

Of importance when selecting a voting method is whether, on a regular basis, its outcomes accurately capture the intent of voters. A surprise is that very few procedures do this. Another desired feature is for a decision approach to assist groups in reaching a consensus (Sect. 5). As described, these goals are satisfied only with the Borda count. Addressing these objectives requires understanding what can go wrong, what causes voting difficulties, and how bad they can be. To avoid technicalities, all of this is illustrated with examples accompanied by references for readers wishing a complete analysis. As shown (Sects. 1–3), most problems reflect a loss of vital information. Understanding this feature assists in showing that the typical description of Arrow’s Theorem, “with three or more alternatives, no voting method is fair,” is not accurate (Sect. 2).

We study the effects of deliberation on collective decisions. In a series of experiments, we vary groups' preference distributions (between common and conflicting interests) and the institutions by which decisions are reached (simple majority, two-thirds majority, and unanimity). Without deliberation, different institutions generate significantly different outcomes, tracking the theoretical comparative statics. Deliberation, however, significantly diminishes institutional differences and uniformly improves efficiency. Furthermore, communication protocols exhibit an array of stable attributes: messages are public, consistently reveal private information, provide a good predictor for ultimate group choices, and follow particular (endogenous) sequencing.

This paper combines dynamic social choice and strategic experimentation to study the following question: How does a society, a committee, or, more generally, a group of individuals with potentially heterogeneous preferences, experiment with new opportunities? Each voter recognizes that, during experimentation, other voters also learn about their preferences. As a result, pivotal voters today are biased against experimentation because it reduces their likelihood of remaining pivotal. This phenomenon reduces equilibrium experimentation below the socially efficient level, and may even result in a negative option value of experimentation. However, one can restore efficiency by designing a voting rule that depends deterministically on time. Another main result is that even when payoffs of a reform are independently distributed across the population, good news about any individual's payoff increases other individuals' incentives to experiment with that reform, due to a positive voting externality.

We consider the credibility, persuasiveness, and informativeness of multidimensional cheap talk by an expert to a decision maker. We find that an expert with state-independent preferences can always make credible comparative statements that trade off the expert's incentive to exaggerate on each dimension. Such communication benefits the expert—cheap talk is \"persuasive\"—if her preferences are quasiconvex. Communication benefits a decision maker by allowing for a more informed decision, but strategic interactions between multiple decision makers can reverse this gain. We apply these results to topics including product recommendations, voting, auction disclosure, and advertising.