Esta tesis ofrece una justificación para el uso de la pluralidad como una manera óptima de agregar información en las sociedades compuestas por individuos con intereses comunes pero con información diversa. El motivo de esta tesis es seguir una línea de investigación sobre la elección social que se remonta al matemático y filósofo político francés Jean-Antoine-Nicolas de Caritat, Marqués de Condorcet (1743-1794). En su Essai sur l'application de l'analyse à la probabilité des decisions rendues à la pluralité des voix (1785), Condorcet afirmó que se garantizaría la justicia social si las naciones adoptaran constituciones políticas que facilitaran el juicio correcto del grupo y argumentó que la votación por mayoría sería la herramienta constitucional más probable para alcanzar este objetivo.Siguiendo esta línea de investigación, la primera parte de esta tesis estudia las condiciones bajo las cuales la pluralidad proporciona a la sociedad el método más adecuado para llegar a decisiones de grupo. Aquí, como en el estudio de Condorcet, supondremos que los votantes actúan honradamente.El desarrollo natural de la teoría de votación, que ha introducido los temas de incentivos e interacción estratégica en la toma de decisiones de grupos, ha sido utilizado para cuestionar la suposición de votación honesta. Austen-Smith y Banks (1996) fueron los primeros en observar que la combinación de información privada e intereses comunes en el sistema propuesto por Condorcet podría crear incentivos para los votantes para actuar estratégicamente. Esta observación les condujo a plantear si la votación honesta sería compatible con el comportamiento de equilibrio de Nash en el juego inducido por la mayoría. La segunda parte de esta tesis expone esta problemática estudiando el comportamiento de los votantes en el juego inducido por la pluralidad.El interés en las instituciones del mundo real, para las cuales la votación es un elemento importante, ha hecho plantear desde hace tiempo la cuestión de si los votantes se comportan tal y como pronostican los modelos teóricos. Otra cuestión ha sido cómo tratar la complejidad del entorno estratégico. La segunda parte de esta tesis pide respuestas a estas preguntas. Puesto que la literatura sobre experimentos de votación parece proporcionar respuestas razonables a estas preguntas, la tercera parte de esta tesis utiliza experimentos de laboratorio para verificar las implicaciones de la segunda parte. / This thesis offers a justification for the use of plurality rule as an optimal way to aggregate information for societies composed of individuals with common interests but diverse information. The motivation of this thesis follows a line of research in social choice that dates back to the French mathematician and political philosopher Jean-Antoine-Nicolas de Caritat, Marquis de Condorcet (1743-1794). In his Essai sur l'application de l'analyse à la probabilité des decisions rendues à la pluralité des voix (1785), Condorcet posited that social justice would be secured if nations would adopt political constitutions that facilitate accurate group judgments, and argued that the majority rule would be the most likely constitutional tool to achieve this goal.Following this line of research, the first part of this thesis discusses the conditions under which plurality rule provides the society with the most likely method to reach accurate group judgments. In this part, as in Condorcet's work, it is assumed that voters act honestly. Natural developments in the theory of voting, that brought in the issues of incentives and strategic interaction in group decision making, were used to challenge the assumption of honest voting. Austen-Smith and Banks (1996) were the first to notice that the combination of private information and common interests in the framework proposed by Condorcet might create an incentive for voters to act strategically. This observation led them to ask the question of whether honest voting is compatible with the Nash equilibrium behavior in the game induced by majority rule. The second part of this thesis advances this problematic by studying voters' behavior in the game induced by plurality rule.The interest in real-world institutions, for which voting is an important element, raised for some time the question of whether voters behave as predicted by the theoretical models. Another question was of how to deal with the complexity of the strategic environment. The second part of this thesis calls for answers to these types of questions. Since the literature on voting experiments seems to provide reasonable answers to these questions, the third part of this thesis uses laboratory experiments to test the implications of the second part.

“Winner-take-all” networks typically pick as winners that alternative with the largest excitatory input. This choice is far from optimal when there is uncertainty in the strength of the inputs, and when information is available about how alternatives may be related. In the Social Choice community, many other procedures will yield more robust winners. The Borda Count and the pair-wise Condorcet tally are among the most favored. Their implementations are simple modifications of classical recurrent networks.

The eighteenth century saw many innovations in political culture including the rise of the public sphere where political ideas were freely and openly discussed and criticized. The new public sphere arose within the institutions of private life such as the Republic of Letters and salons, so the modes of behavior in private life were important influences on the new political culture of the public sphere. By studying the lives and careers of Richard Price and the Marquis de Condorcet, I examine the role that the private institution of friendship played in the new political culture of the late Enlightenment. During the 1780s, friendship became an important political symbol that represented the enlightened ideals of equality, reciprocity, liberty, and humanitarianism.

Cette thèse a pour enjeu de traiter des paradoxes étudiés en théorie du choix social.Le paradoxe d'Ostrogorski sur deux axes programmatiques a été traité, notamment sa probabilité de réalisation par l'ajout d'un critère discriminant sur les axes au moment de réaliser le choix de l'électeur : une formule de calcul exacte a été mise au point pour des valeurs de population finies afin de mesurer son occurrence pour différents effectifs, et une borne maximale émerge autours de 0,085.Parmi, les différentes anomalies étudiées en théorie du choix social affectant le fonctionnement des démocraties, le paradoxe du référendum occupe une place particulière du fait de son observation assez récurrente dans l'histoire électorale récente.L'un des enjeux de cette thèse a été de déterminer une méthode utilisable pour mesurer précisément sa probabilité d'occurrence dans des conditions précises de taille du corps électoral et de découpage.Il a été notamment recherché un moyen de comparer sa fréquence selon le nombre de circonscriptions retenu.Une formule a ainsi été déterminée pour des découpage du corps électoral en 3, 5, 7 et 9 circonscriptions de taille homogène.Un second résultat de la thèse sur le même paradoxe a été d'abolir l'hypothèse d'homogénéité parfaite des effectifs des circonscriptions pour mesurer l'effet de leur variation sur la probabilité de conflit pour un découpage en 3 circonscriptions.Des pistes ultérieures de recherche ont également explorées, en particulier la possibilité d'abolir partiellement l'hypothèse de culture neutre avec un découpage en 3 circonscriptions.Il a également été procédé à un état des lieux des types d'architecture institutionnelle, dont une classification globale en quatre catégories a été établie.Il a été tenté de déterminer leur poids dans les conflits de pouvoirs observés dans certains pays, en ayant notamment recours à des résultats obtenus grâce au paradoxe du référendum. / This thesis has aimed issues to deal with paradoxes studied in social choice theory.The Ostrogorski paradox with two programmatic axes was treated, including its achievement by adding a distinguishing criterion on the axes to realize the voter choice: an exact formula has been developed for a finite population to measure its occurrence for different numbers, and a effective maximum bound has emerged around 0.085.Among the various anomalies studied in social choice theory in the functioning of democracy, the referendum paradox holds a special place because of its fairly recurrent observation in recent electoral history.One of the stake of this thesis was to determine a suitable method to accurately measure its probability of occurrence in precise terms of size of the electorate and cutting.It was particularly sought a way to compare its frequency depending on the number of selected districts.A formula has been determined for cutting the electorate in 3, 5, 7 and 9 homogeneous size constituencies.A second result of the thesis on the same paradox was to relax the perfect homogeneity assumption on the constituencies size to measure the effect of their variation on the likelihood of conflict for a division into 3 districts.Subsequent research directions have also explored the possibility to partially abolish the assumption of impartial culture with a division into three districts.An inventory has been also conducted of the institutional architecture types.A comprehensive four-category classification was established, and we have tried to determine their weight in conflicts of powers observed in some countries,in particular using results deduced from the referendum paradox.

A la mort de Voltaire, une équipe d’admirateurs du patriarche fonde la « Société Littéraire Typographique » pour réaliser une nouvelle édition complète de son œuvre. Ce projet dissident et pionnier, réalisé sous la direction de Beaumarchais et de Condorcet dans la clandestinité, s’inscrit dans la perspective d’une diffusion militante des textes et des idées des Lumières. Malgré les innombrables obstacles qui s’opposent à cette entreprise subversive, les correspondants de la SLT parviennent à « finir ce cher Voltaire » et livrent à la postérité, entre 1785 et 1790, une édition in octavo en 70 volumes et une édition in-Douze en 90 volumes. Cette édition posthume et intégrale de l’œuvre de Voltaire constitue une première dans le champ éditorial français, à la fois par le luxe et le soin apporté à l’édition « chef d’œuvre de l’art typographique » mais aussi par l’apport de la correspondance, qui livre l’image de l’homme privé et même intime, à côté de l’œuvre littéraire. Le dernier volume, intitulé Vie de Voltaire, est le texte qui relie les deux ensembles. Pour Condorcet, Voltaire a fait de sa vie un chef d’œuvre, qu’il s’agit de livrer à la postérité pour sa valeur morale et politique. Au-Delà de son caractère exemplaire, cette édition pose de nombreuses questions, historiques, philologiques et idéologiques qui touchent à l’histoire du livre, à la connaissance du corpus voltairien, à l’enjeu politique et idéologique majeur que représente l’œuvre de Voltaire dans le contexte très polémique des années pré-Révolutionnaires, au mythe littéraire édifié par cette entreprise éditoriale, et à la réception de l’œuvre ainsi rendue publique. / Upon Voltaire’s death, a group of enlightened admirers of the patriarch founded the « Société Littéraire Typographique » with the aim of publishing a new complete edition of his works. This subversive and pioneering project, directed by Beaumarchais and Condorcet in clandestinity, was aimed at disseminating the texts and ideas of the Enlightenment. Despite the innumerous obstacles standing in the way of this subversive entreprise, the correspondents of the SLT were able to complete « ce cher Voltaire » and deliver to posterity, between 1785 and 1790, an edition in-Octavo in 70 volumes and an edition in-12° in 90 volumes. This complete posthumous edition of Voltaire’s works was a first in the French publishing, both for the luxury and the care which caracterized the realization of the book, « a masterpiece of typographical art » and the correspondence, in which we can see an image of the private man and his intimacy, beside his literary writings. The last volume, the Vie de Voltaire, is the textum and the link between these two parts. For Condorcet, Voltaire had transformed his life into a masterpiece, which the editors wanted to show to posterity for its political and moral value. In addition to its exemplarity, this edition raises many historical, philological and ideological questions related to book history, to the knowledge of the Voltairian corpus, to the major political and ideological issues portrayed in Voltaire’s writings in the very polemical context of pre-Revolutionay times, to the literary myth created by this editorial enterprise, and to the reception of his writings thus made public

Chapter 1 : I attempt a detailed literature review on the passage from the probabilistic versions of the Condorcet Jury Theorem to models augmented by the concept of strategic agents, including both theoretical and relevant empirical work. In the first part, I explore the most influential relevant game theoretic models and their main predictions. In the second part, I review what voting experiments have to say about these predictions, with a brief mention of the experiments' key methodological aspects. In the final part, I provide with an attempt to map the recent strategic voting literature in terms of structure and scope. I close with a philosophical question on the exogeneity of a "correct" choice of a voting outcome, which is inherent in the current strategic voting literature. Chapter 2 : I develop a two stage game with individually costly political action and costless voting on a binary agenda where, in equilibrium, agents rationally cast honest votes in the voting stage. I show that a positive but sufficiently low individual cost of political action can lead to a loss in aggregate welfare for any electorate size. When the individual cost of political action is lower than the signalling gain, agents will engage in informative political action. In the voting stage, since everyone's signal is revealed, agents will unanimously vote for the same policy. Therefore, the result of the ballot will be exactly the same as the one without prior communication, but with the additional aggregate cost of political action. However, when agents have heterogeneous prior beliefs, society is large and the state of the world is sufficiently uncertain, a moderate individual cost of political action can induce informative collective action of only a subset of the members of society, which increases ex ante aggregate welfare relative to no political action. The size of the subset of agents engaging in collective action depends on the dispersion of prior opinions. Chapter 3 : This chapter shows theoretically that hearing expert opinions can be a double-edged sword for decision making committees. We study a majoritarian voting game of common interest where committee members receive not only private information, but also expert information that is more accurate than private information and observed by all members. We identify three types of equilibria of interest, namely i) the symmetric mixed strategy equilibrium where each member randomizes between following the private and public signals should they disagree; ii) the asymmetric pure strategy equilibrium where a certain number of members always follow the public signal while the others always follow the private signal; and iii) a class of equilibria where a supermajority and hence the committee decision always follow the expert signal. We find that in the first two equilibria, the expert signal is collectively taken into account in such a way that it enhances the efficiency (accuracy) of the committee decision, and a fortiori the CJT holds. However, in the third type of equilibria, private information is not reflected in the committee decision and the efficiency of committee decision is identical to that of public information, which may well be lower than the efficiency the committee could achieve without expert information. In other words, the introduction of expert information might reduce efficiency in equilibrium. Chapter 4 : In this chapter we present experimental results on the theory of the previous chapter. In the laboratory, too many subjects voted according to expert information compared to the predictions from the efficient equilibria. The majority decisions followed the expert signal most of the time, which is consistent with the class of obedient equilibria mentioned in the previous chapter. Another interesting finding is the marked heterogeneity in voting behaviour. We argue that the voters' behaviour in our data can be best described as that in an obedient equilibrium where a supermajority (and hence the decision) always follow the expert signal so that no voter is pivotal. A large efficiency loss manifests due to the presence of expert information when the committee size was large. We suggest that it may be desirable for expert information to be revealed only to a subset of committee members. Finally, in the Appendix we describe a new alternative method for producing the signal matrix of the game. Chapter 5 : There is a significant gap between the theoretical predictions and the empirical evidence about the efficiency of policies in reducing crime rates. This chapter argues that one important reason for this is that the current literature of economics of crime overlooks an important hysteresis effect in criminal behaviour. One important consequence of hysteresis is that the effect on an outcome variable from positive exogenous variations in the determining variables has a different magnitude from negative variations. We present a simple model that characterises hysteresis in both the micro and macro levels. When the probability of punishment decreases, some law abiding agents will find it more beneficial to enter a criminal career. If the probability of punishment returns to its original level, a subset of these agents will continue with their career in crime. We show that, when crime choice exhibits weak hysteresis at the individual level, crime rate in a society consisted from a continuum of agents that follows any non-uniform distribution will exhibit strong hysteresis. Only when punishment is extremely severe the effect of hysteresis ceases to exist. The theoretical predictions corroborate the argument that policy makers should be more inclined to set pre-emptive policies rather than mitigating measures.

Whereas benchmarking experiments are very frequently used to investigate the performance of statistical or machine learning algorithms for supervised and unsupervised learning tasks, overall analyses of such experiments are typically only carried out on a heuristic basis, if at all. We suggest to determine winners, and more generally, to derive a consensus ranking of the algorithms, as the linear order on the algorithms which minimizes average symmetric distance (Kemeny-Snell distance) to the performance relations on the individual benchmark data sets. This leads to binary programming problems which can typically be solved reasonably efficiently. We apply the approach to a medium-scale benchmarking experiment to assess the performance of Support Vector Machines in regression and classification problems, and compare the obtained consensus ranking with rankings obtained by simple scoring and Bradley-Terry modeling. / Series: Research Report Series / Department of Statistics and Mathematics

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Le but de ce travail est essentiellement de faire une étude géologique et métallogénique d'une région donnée . La méthode choisie est en principe de noter d'abord les grands traits géologiques et ensuite d'essayer de résoudre les problèmes métallogéniques qui y sont liés. Le terrain principal et typique de nos recherches se trouve à Condorcet (Drôme). D'autres localités ont été choisies à l'Argentière (Basses-Alpes) et à Orpierre (Drôme) et, par comparaison, quelques remarques ont été faites sur Propiac (Drôme). Ces localités sont toutes situées dans les Baronnies.

This dissertation consists of three essays on information aggregation in committees and its application. The first essay analyzes how the distribution of votes affects the accuracy of group decisions. In a weighted voting system, votes are typically assigned based on the criteria that are unrelated to the voters’ ability to make a correct judgment. I introduce an information aggregation model in which voters are identical except for voting shares. If the information is free, the optimal weight distribution is equal weighting. When acquiring information is costly, by contrast, I show that the accuracy of group decisions may be higher under some weighted majority rules than under unweighted majority rule. I characterize the equilibrium and find the optimal weight distribution to maximize the accuracy of group decisions. Asymmetric weight distributions may be optimal when the cost of improving signal is moderately high. The second essay analyzes how intergenerational family transfers can be sustained. Why are generous transfers from the younger to the older generations made in some families and not in others? My paper argues that differences in intergenerational dependence are due to variation in community networks. My analysis of the sustainability of intergenerational transfers posits game theoretical models of overlapping generations in which breadwinners make transfers to their parents and children. A novel feature of my models is that there is a local community that may supply information about its members past behaviors. I demonstrate that an efficient level of intergenerational transfers can be sustained if neighbors gossip about each other. The third essay, co-authored with Fuhito Kojima, investigates a jury decision when hung juries and retrials are possible. When jurors in subsequent trials know that previous trials resulted in hung juries, informative voting can be an equilibrium if and only if the accuracy of signals for innocence and guilt are exactly identical. Moreover, if jurors are informed of numerical split of votes in previous trials, informative voting is not an equilibrium regardless of signal accuracy. / Government