Condorcet Jury Research Articles

Justifying political choice: from probability and institutions to communication

The article is devoted to the study of the dynamics of development of concepts that justify political choice. There is a general turn from the moral justification of political choice to ontological concepts based on the ideas of pragmatic and impartial behavior in the search for criteria for the “correct” decision, which includes the truth and the institutions that ensure it. The epistemic concept of democracy, based on Condorcet's jury theorem, defines the possibility of achieving the correct choice through majority rule voting, implies a competent, independent and sincere voter, which ensures an increase in the probability of the correct choice. The expansion of the composition of participants in political choice increased the role of diversity of knowledge and opinions in the justification, which led to the concept of the “smart plurality”, which ensures the correct choice is made by reducing its overall error through random mass participation. The development of social networks and their argumentative function in disputes have contributed to the transition to the concepts of argumentative networks that ensure the correct option is selected through communication. The identified dynamics allow us to conclude that the concept of politics is reviving its importance as a reasoning.

An Interpretation of Weights in Linear Opinion Pooling

AbstractThis paper explores the fact that linear opinion pooling can be represented as a Bayesian update on the opinions of others. It uses this fact to propose a new interpretation of the pooling weights. Relative to certain modelling assumptions the weights can be equated with the so-called truth-conduciveness known from the context of Condorcet's jury theorem. This suggests a novel way to elicit the weights.

Ансамбль нейромереж GRNN на підставі зміщених поверхонь відгуку для задач електронної комерції

Розв'язок задач електронної комерції, які здебільшого характеризуються нелінійними поверхнями відгуку, є важливим завданням. Застосування сучасних засобів обчислювального інтелекту не завжди є доречним зважаючи на складність реалізації процедур навчання і налагодження. Неітеративні засоби та нейронні мережі без навчання також не забезпечують задовільної точності результату. З огляду на це у роботі описано новий ансамбль на підставі нейронних мереж узагальненої регресії. Основна ідея розробленого ансамблю полягає в лінеаризації поверхні відгуку, що задається даними наявної вибірки. Для цього отримана за допомогою мережі GRNN поверхня подається на вхід лінійної нейроподібної структури. Така комбінація забезпечує підвищення точності роботи ансамблю під час розв'язання поставленої задачі. Описаний ансамбль застосовано для розв'язання задачі прогнозування ціни на вживані автомобілі. Експериментальним способом підібрано оптимальні параметри його роботи. Шляхом порівняння із відомими методами встановлено найвищу точність його роботи. Результати експериментальних досліджень порівняно з теоретичними оцінками на підставі висновків теореми Кондорсе про журі присяжних. Розроблений ансамбль нейронних мереж узагальненої регресії на підставі зміщення поверхонь відгуку та з додатковим використанням нейроподібних структур Моделі послідовних геометричних перетворень варто застосовувати під час розв'язання різноманітних задач електронної комерції підвищеної точності.

How Communication Can Make Voters Choose Less Well.

With the advent of social media, the last decade has seen profound changes to the way people receive information. This has fueled a debate about the ways (if any) changes to the nature of our information networks might be affecting voters' beliefs about the world, voting results, and, ultimately, democracy. At the same time, much discussion in the public arena in recent years has concerned the notion that ill-informed voters have been voting against their own self-interest. The research reported here brings these two strands together: simulations involving agent-based models, interpreted through the formal framework of Condorcet's (1785) jury theorem, demonstrate how changes to information networks may make voter error more likely, even though individual competence has largely remained unchanged.

One standard to rule them all?

AbstractIt has been argued that an epistemically rational agent's evidence is subjectively mediated through some rational epistemic standards, and that there are incompatible but equally rational epistemic standards available to agents. This supports Permissiveness, the view according to which one or multiple fully rational agents are permitted to take distinct incompatible doxastic attitudes towards P (relative to a body of evidence). In this paper, I argue that the above claims entail the existence of a unique and more reliable epistemic standard. My strategy relies on Condorcet's Jury Theorem. This gives rise to an important problem for those who argue that epistemic standards are permissive, since the reliability criterion is incompatible with such a type of Permissiveness.

Integrating spatial, morphological, and textural information for improved cell type differentiation using Raman microscopy

AbstractRaman microscopy is a well‐established tool for distinguishing different cell types in cell biological or cytopathological applications, since it can provide maps that show the specific distribution of biochemical components in the cell, with high lateral and spatial resolution. Currently, established data analysis approaches for differentiating cells of different types mostly rely on conventional chemometrics approaches, which tend to not systematically utilise the advantages provided by Raman microscopic data sets. To address this, we propose 2 approaches that explicitly exploit the large number of spectra as well as the morphological and textural information that are available in Raman microscopic data sets. Spatial bagging as our first approach is based on a statistical analysis of majority vote over classification results obtained from individual pixel spectra. Based on the Condorcet's Jury Theorem, this approach raises the accuracy of a relatively weak classifier for individual spectra to nearly perfect accuracy at the level of characterising whole cells. Our second approach extracts morphological and textural (morpho‐textural) features from Raman microscopic images to differentiate cell types. While using few wavenumbers of the Raman spectrum only, our results indicate on a quantitative basis that Raman microscopic images carry more morphological and textural information than haematoxylin and eosin (H&E) stained images as the current gold standard in cytopathology. Our 2 approaches promise improved protocols for the fast acquisition of Raman imaging data, for instance, for the morphological analysis of coherent anti‐Stokes Raman spectroscopy microscopic imaging data or for improving the accuracy of fibre optical probe systems by resampling spectra and utilising spatial bagging.

The wisdom of crowds: What do citizens forecast for the 2015 British General Election?

Who do you think will win in your constituency? Most citizens correctly answer this question, and groups are even better at answering it. Combining individual forecasts results in the ‘wisdom of crowds’ explained by Condorcet's jury theorem. This paper demonstrates the accuracy of citizen forecasts in seven British General Elections between 1964 and 2010, and reports what citizens interviewed in February and March forecasted for the election in May 2015. ‘Citizen forecasting’ predicts vote shares and winners in constituency elections, and seat numbers and governments in national elections. The paper also introduces a new method for predicting vote shares from citizen forecasts. Citizen forecasts are direct, accurate, and comprehensible. Pollsters should collect them and communicate their results more often.

Monetary Policy Deliberations : Committee Size and Voting Rules

How large should a monetary policy committee be? Which voting rule should a monetary policy committee adopt? This paper builds on Condorcet's jury threorem to analyse the relationships between committee size and voting rules in a model where policy discussions are subject to a time constraint. It suggests that in large committees majority voting is likely to enhance policy outcomes. Under unanimity (consensus) it is preferable to limit the size of the committee. Finally, supermajority voting rules are social contrivances that contribute to policy performance in a more uncertain environment, when initial policy proposals are less likely to be correct, or when payoffs are asymmetric.

Are two interviewers better than one?

How many interviewers per job applicant are necessary for a company to achieve the highest hit rate? Are two better than one? Condorcet's Jury Theorem and the “wisdom of the crowd” suggest that more is better. Under quite general conditions this study shows, surprisingly, that two interviewers are on average not superior to the best interviewer. Adding further interviewers will also not increase the expected collective hit rate when interviewers are homogeneous (i.e., their hits are nested), only doing so when interviewers are heterogeneous (i.e., their hits are not nested). The current study shows how these results depend on the number of interviewers, their expertise, and the chance of free riding, and specify the conditions when “less is more”. This analysis suggests that the best policy is to invest resources into improving the quality of the best interviewer rather than distribute these to improve the quality of many interviewers.

Monetary Policy Deliberations: Committee Size and Voting Rules

SummaryHow large should a monetary policy committee be? Which voting rule should a monetary policy committee adopt? This paper builds on Condorcet's jury theorem to analyse the relationships between committee size and voting rules in a model where policy discussions are subject to a time constraint. It suggests that in large committees majority voting is likely to enhance policy outcomes. Under unanimity (consensus) it is preferable to limit the size of the committee. Finally, supermajority voting rules are social contrivances that contribute to policy performance in a more uncertain environment, when initial policy proposals are less likely to be correct, or when payoffs are asymmetric.

Monetary Policy Deliberations: Committee Size and Voting Rules

How large should a monetary policy committee be? Which voting rule should a monetary policy committee adopt? This paper builds on Condorcet's jury threorem to analyse the relationships between committee size and voting rules in a model where policy discussions are subject to a time constraint. It suggests that in large committees majority voting is likely to enhance policy outcomes. Under unanimity (consensus) it is preferable to limit the size of the committee. Finally, supermajority voting rules are social contrivances that contribute to policy performance in a more uncertain environment, when initial policy proposals are less likely to be correct, or when payoffs are asymmetric. JEL Classification: D71, D78, D81, E58

Social Choice: Equilibrium or Catastrophe

This paper surveys results in general equilibrium theory based on dynamical models, and emphasizes role of structural stability. In this context it is natural to consider a preference field H for society, combining economic fields, associated with preferred changes wrought by agents in economic market place, together with fields of preferred changes in polity. A condition called half-openness of H is sufficient to guarantee existence of a local direction gradient,d, for society, and thus of a social choice. The condition is equivalent to a dual property that dual co-cones of H have non-empty intersection. This result is analogous to Chichilnisky's necessary and sufficient condition for market equilibrium.We then consider models of belief aggregation similar to Condorcet's Jury theorem. The half open property may fail for general dynamical processes and this feature is linked to creation of belief cascades. Finally, Thom's notion of a structurally stable chreod is introduced. Even when a belief or preference field is locally chaotic because of a failure of half openness, it is possible to define a generalized social correspondence called heart. The heart is lower hemi-continuous and is characterized by a possible rapid expansion at a critical value of parameters. It is suggest that events in heart obey a power law distribution as is generally associated with the edge of chaos.

Estimating juror accuracy, juror ability, and the relationship between them.

This article advances a method based on standard test theories and measurement models to determine correct verdicts for jury trials, and to estimate juror accuracy, juror ability, and trial difficulty (and the relationships among them). With five vignette cases and 1,318 juror eligible adults as the subjects, the model consistently identified verdicts that accorded with the judge's instructions on the law as correct. With the correct verdicts, the strength of the relationship between juror accuracy and juror ability was found to be substantial. These findings suggest that the assumption of equivalent accuracy of jurors underlying the Condorcet's jury theorem (Condorcet, Essai sur l'Application de l'Analyse a la Probabilite des Decisions Rendues a la Pluralite des Voix, Paris, 1785) may be untenable for general cases where jurors of diverse dispositions and abilities serve together; and that the role of juror ability in determining the accuracy of legal decisions could be more significant than that of attitudes and values because, unlike attitudes and values, ability could affect juror's legal decisions regardless of the type of the case.

Social Choice and Catastrophe

This paper surveys results in general theory based on dynamical models, and emphasizes role of structural stability. In this context it is natural to consider a preference field H for society, combining economic fields, associated with preferred changes wrought by agents in economic market place, together with fields of preferred changes in polity. A condition called half-openness of H is sufficient to guarantee existence of a local direction gradient,d, for society, and thus of a social choice. The condition is equivalent to a dual property that dual co-cones of H have non-empty intersection. This result is analogous to Chichilnisky's necessary and sufficient condition for market equilibrium.We then consider models of belief aggregation similar to Condorcet's Jury theorem and mention Penn's Theorem on existence of a belief equilibrium. The half open property may fail for general dynamical processes and this feature is linked to creation of belief cascades at of Some comments are addressed to notion of punctuated equilibrium in evolutionary models in biology and language. Finally, Thom's notion of a structurally stable chreod is introduced. Even when a belief or preference field is locally chaotic because of a failure of half openness, it is possible to define a generalized social correspondence called heart. The heart is lower hemi-continuous and is characterized by a possible rapid expansion at a critical value of parameters. It is suggest that events in heart obey a power law distribution which is generally associated with the edge of chaos.

Condorcet's Jury Theorem and the Optimum Number of Voters

Many political theorists and philosophers use Condorcet's Jury Theorem to defend democracy. This article illustrates an uncomfortable implication of Condorcet's Jury Theorem. Realistically, when the conditions of Condorcet's Jury Theorem hold, even in very high stakes elections, having more than 100,000 citizens vote does no significant good in securing good political outcomes. On the Condorcet model, unless voters enjoy voting, or unless they produce some other value by voting, then the cost to most voters of voting exceeds the expected epistemic benefits to the common good of their casting a vote. Anyone who is committed to democracy on the basis of the Jury Theorem ought also to hold that widespread voting is wasteful, at least unless he or she can provide some further justification of mass democratic participation.

Independence and interdependence in collective decision making: an agent-based model of nest-site choice by honeybee swarms

Condorcet's jury theorem shows that when the members of a group have noisy but independent information about what is best for the group as a whole, majority decisions tend to outperform dictatorial ones. When voting is supplemented by communication, however, the resulting interdependencies between decision makers can strengthen or undermine this effect: they can facilitate information pooling, but also amplify errors. We consider an intriguing non-human case of independent information pooling combined with communication: the case of nest-site choice by honeybee (Apis mellifera) swarms. It is empirically well documented that when there are different nest sites that vary in quality, the bees usually choose the best one. We develop a new agent-based model of the bees' decision process and show that its remarkable reliability stems from a particular interplay of independence and interdependence between the bees.

The Premises of Condorcet's Jury Theorem Are Not Simultaneously Justified

ABSTRACTCondorcet's famous jury theorem reaches an optimistic conclusion on the correctness of majority decisions, based on two controversial premises about voters: they are competent and vote independently, in a technical sense. I carefully analyse these premises and show that: (i) whether a premise is justified depends on the notion of probability considered and (ii) none of the notions renders both premises simultaneously justified. Under the perhaps most interesting notions, the independence assumption should be weakened.

Informational limits to democratic public policy: The jury theorem, yardstick competition, and ignorance

Condorcet's jury theorem provides a possible explanation for the success of democracies relative to other forms of governance since the late industrial revolution. In its modern form, the jury theorem predicts that majority decisions will be well informed, because they are based on far more information than possessed by any single voter. On the other hand, it is evident that democratic politicians and policies are not always as good as the jury theorem implies they should be. This paper uses simulations to explore the power and limitations of majority rule as an estimator of candidate or policy effectiveness. The simulations demonstrate that a moderate number of slightly informed voters can make very accurate choices among candidates using majority rule. However, voter ignorance can nonetheless be a significant problem for the accuracy of majority decisions.

Informational Limits to Democratic Public Policy: The Jury Theorem, Yardstick Competition, and Ignorance

Condorcet's jury theorem provides a possible explanation for the success of democracies relative to other forms of governance since the late industrial revolution. In its modern form, the jury theorem predicts that majority decisions will be well informed, because they are based on far more information than possessed by any single voter. On the other hand, it is evident that democratic politicians and policies are not always as good as the jury theorem implies they should be. This paper uses simulations to explore the power and limitations of majority rule as an estimator of candidate or policy effectiveness. The simulations demonstrate that a moderate number of slightly informed voters can make very accurate choices among candidates using majority rule. However, voter ignorance can nonetheless be a significant problem for the accuracy of majority decisions.

No Testimonial Route to Consensus

ABSTRACTThe standard image of how consensus can be achieved is by pooling evidence and reducing if not eliminating disagreements. But rather than just pooling substantive evidence on a certain question, why not also take into account the formal, testimonial evidence provided by the fact that a majority of the group adopt a particular answer? Shouldn't we be reinforced by the discovery that we are on that majority side, and undermined by the discovery that we are not? Shouldn't this be so, in particular, when Condorcet's jury theorem applies? It turns out not. There are serious problems attending any strategy of majoritarian deference.