Models of Political Economy

Models of Political Economy will introduce students to the basic methodology of political economics. It covers all core theories as well as new developments including: decision theory game theory mechanism design games of asymmetric information. Hannu Nurmi's text will prove to be invaluable to all students who wish to understand this increasingly technical field

Vers des modes de scrutin moins manipulables

We study coalitional manipulation of voting systems: can a subset of voters, by voting strategically, elect a candidate they all prefer to the candidate who would have won if all voters had voted truthfully? From a theoretical point of view, we develop a formalism which makes it possible to study all voting systems, whether the ballots are orders of preference on the candidates (ordinal systems), ratings or approval values (cardinal systems), or even more general objects. We show that for almost all classical voting systems, their manipulability can be strictly reduced by adding a preliminary test aiming to elect the Condorcet winner if there is one. For the other voting systems, we define the generalized Condorcification which leads to similar results. Then we define the notion of decomposable culture, an assumption of which the probabilistic independence of voters is a special case. Under this assumption, we prove that, for each voting system, there exists a voting system which is ordinal, shares certain properties with the original voting system, and is at most as manipulable. Thus, the search for a voting system of minimal manipulability (in a class of reasonable systems) can be restricted to those which are ordinal and satisfy the Condorcet criterion. In order to allow everyone to examine these phenomena in practice, we present SVVAMP, a Python package of our own dedicated to the study of voting systems and their manipulability. Then we use it to compare the coalitional manipulability of various voting systems in several types of cultures, i.e. probabilistic models that generate populations of voters equipped with random preferences. We then complete the analysis with elections from real experiments. Finally, we determine the voting systems with minimal manipulability for very low values of the number of voters and of the number of candidates, and we compare them with the classical voting systems of the literature. In general, we establish that Borda's method, Range voting, and Approval voting are particularly manipulable. Conversely, we show the excellent resistance to manipulation of the system called IRV, also known as STV, and of its variant Condorcet-IRV.Nous étudions la manipulation par coalition des modes de scrutin: est-ce qu'un sous-ensemble des électeurs, en votant de façon stratégique, peut faire élire un candidat qu'ils préfèrent tous au candidat qui aurait été vainqueur si tous les électeurs avaient voté sincèrement? D'un point de vue théorique, nous développons un formalisme qui permet d'étudier tous les modes de scrutin, que les bulletins soient des ordres de préférences sur les candidats (systèmes ordinaux), des notes ou des valeurs d'approbation (systèmes cardinaux) ou des objets encore plus généraux. Nous montrons que pour la quasi-totalité des modes de scrutin classiques, on peut réduire strictement leur manipulabilité en ajoutant un test préliminaire visant à élire le vainqueur de Condorcet s'il en existe un. Pour les autres modes de scrutin, nous définissons la condorcification généralisée qui permet d'obtenir des résultats similaires. Puis nous définissons la notion de culture décomposable, une hypothèse dont l'indépendance probabiliste des électeurs est un cas particulier. Sous cette hypothèse, nous prouvons que, pour tout mode de scrutin, il existe un mode de scrutin qui est ordinal, qui partage certaines propriétés avec le mode de scrutin original et qui est au plus aussi manipulable. Ainsi, la recherche d'un mode de scrutin de manipulabilité minimale (dans une classe de systèmes raisonnables) peut être restreinte à ceux qui sont ordinaux et vérifient le critère de Condorcet. Afin de permettre à tous d'examiner ces phénomènes en pratique, nous présentons SVVAMP, un package Python de notre cru dédié à l'étude des modes de scrutin et de leur manipulabilité. Puis nous l'utilisons pour comparer la manipulabilité par coalition de divers modes de scrutin dans plusieurs types de cultures, c'est-à-dire des modèles probabilistes permettant de générer des populations d'électeurs munis de préférences aléatoires. Nous complétons ensuite l'analyse avec des élections issues d'expériences réelles. Enfin, nous déterminons les modes de scrutin de manipulabilité minimale pour de très faibles valeurs du nombre d'électeurs et du nombre de candidats et nous les comparons avec les modes de scrutin classiques. De manière générale, nous établissons que la méthode de Borda, le vote par notation et le vote par assentiment sont particulièrement manipulables. À l'inverse, nous montrons l'excellente résistance à la manipulation du système appelé VTI, également connu par son acronyme anglophone STV ou IRV, et de sa variante Condorcet-VTI

Democracy and the Common Good: A Study of the Weighted Majority Rule

In this study I analyse the performance of a democratic decision-making rule: the weighted majority rule. It assigns to each voter a number of votes that is proportional to her stakes in the decision. It has been shown that, for collective decisions with two options, the weighted majority rule in combination with self-interested voters maximises the common good when the latter is understood in terms of either the sum-total or prioritarian sum of the voters’ well-being. The main result of my study is that this argument for the weighted majority rule — that it maximises the common good — can be improved along the following three main lines. (1) The argument can be adapted to other criteria of the common good, such as sufficientarian, maximin, leximin or non-welfarist criteria. I propose a generic argument for the collective optimality of the weighted majority rule that works for all of these criteria. (2) The assumption of self-interested voters can be relaxed. First, common-interest voters can be accommodated. Second, even if voters are less than fully competent in judging their self-interest or the common interest, the weighted majority rule is weakly collectively optimal, that is, it almost certainly maximises the common good given large numbers of voters. Third, even for smaller groups of voters, the weighted majority rule still has some attractive features. (3) The scope of the argument can be extended to decisions with more than two options. I state the conditions under which the weighted majority rule maximises the common good even in multi-option contexts. I also analyse the possibility and the detrimental effects of strategic voting. Furthermore, I argue that self-interested voters have reason to accept the weighted majority rule

Social Choice for Partial Preferences Using Imputation

Within the field of multiagent systems, the area of computational social choice considers the problems arising when decisions must be made collectively by a group of agents. Usually such systems collect a ranking of the alternatives from each member of the group in turn, and aggregate these individual rankings to arrive at a collective decision. However, when there are many alternatives to consider, individual agents may be unwilling, or unable, to rank all of them, leading to decisions that must be made on the basis of incomplete information. While earlier approaches attempt to work with the provided rankings by making assumptions about the nature of the missing information, this can lead to undesirable outcomes when the assumptions do not hold, and is ill-suited to certain problem domains. In this thesis, we propose a new approach that uses machine learning algorithms (both conventional and purpose-built) to generate plausible completions of each agent’s rankings on the basis of the partial rankings the agent provided (imputations), in a way that reflects the agents’ true preferences. We show that the combination of existing social choice functions with certain classes of imputation algorithms, which forms the core of our proposed solution, is equivalent to a form of social choice. Our system then undergoes an extensive empirical validation under 40 different test conditions, involving more than 50,000 group decision problems generated from real-world electoral data, and is found to outperform existing competitors significantly, leading to better group decisions overall. Detailed empirical findings are also used to characterize the behaviour of the system, and illustrate the circumstances in which it is most advantageous. A general testbed for comparing solutions using real-world and artificial data (Prefmine) is then described, in conjunction with results that justify its design decisions. We move on to propose a new machine learning algorithm intended specifically to learn and impute the preferences of agents, and validate its effectiveness. This Markov-Tree approach is demonstrated to be superior to imputation using conventional machine learning, and has a simple interpretation that characterizes the problems on which it will perform well. Later chapters contain an axiomatic validation of both of our new approaches, as well as techniques for mitigating their manipulability. The thesis concludes with a discussion of the applicability of its contributions, both for multiagent systems and for settings involving human elections. In all, we reveal an interesting connection between machine learning and computational social choice, and introduce a testbed which facilitates future research efforts on computational social choice for partial preferences, by allowing empirical comparisons between competing approaches to be conducted easily, accurately, and quickly. Perhaps most importantly, we offer an important and effective new direction for enabling group decision making when preferences are not completely specified, using imputation methods

Mayorías basadas en diferencias: análisis de la consistencia y extensiones

En esta tesis se estudian las mayorías por diferencia de votos y por diferencia de apoyo. Los capítulos 1 y 2 se centran en el análisis de la transitividad y de la triple-aciclicidad de la relación de preferencia fuerte generada por las mayorías por diferencia de apoyo, al agregar relaciones de preferencia recíprocas individuales. En el capítulo 3 se estiman las probabilidades con las que se producen resultados colectivos consistentes, tanto en las mayorías por diferencia de apoyo como en las mayorías por diferencia de votos. En el capítulo 4 se extienden las mayorías por diferencia de votos al contexto de las preferencias lingüísticas, a través de conjuntos difusos y del modelo de las 2-tuplas; se justifica la equivalencia entre ambas modelizaciones bajo determinadas condiciones de regularidad y se estudian las propiedades que cumplen estas mayorías lingüísticasDepartamento de Economía Aplicad

E.G. West and state intervention in education : a philosophical exploration

ABSTRACT: E.G. West raises, but does not adequately address, philosophical issues concerning the justification for state intervention in education. West's market model is outlined, and likely objections - based on recent arguments against 'internal markets' in education - are explored. Chapter 1 outlines West's role for the state in inspecting a 'minimum adequate education for all'. Chapter 2 examines whether this could overcome the objection that markets won't satisfy equality of opportunity. Williams', Rawls' and Dworkin's arguments on equality are found compatible with West's model. The curriculum for West's model is then investigated: Chapter 3 considers 'education for democracy', and whether compulsion is needed to ensure the desired qualities for democratic participation emerge, or whether they could emerge freely in civil society. A reductio ad absurdum argument brings out the illiberal consequence of a compulsory curriculum, of a 'fitness test' for democratic participation. Chapter 4 explores 'education for autonomy'. John White's argument for a compulsory curriculum for autonomy could undermine other autonomy-promoting institutions in civil society, it is suggested. White's argument depends upon Joseph Raz's argument for state promotion of autonomy, which is explored, raising the 'epistemic argument' for markets. John Gray's argument to this effect is extended, to suggest that there will be difficulties with any 'fleshing out' of West's curriculum if it is to be promoted by the state. One way around this, democratic control of the curriculum, is explored in chapter 5. Difficulties with John White's approach arise because of logical constraints on improving democracy, raised by consideration of social choice theory (Arrow's theorem and its corollaries) and public choice theory (logrolling). Chapter 6 considers the objection to markets that education is a 'public good', using the arguments of Gerald Grace and Ruth Jonathan. These are put in the context of the game. theory literature of De Jasay, Taylor, and Axelrod. The 'public goods dilemma' is explored, to arrive at less pessimistic conclusions about markets in education than the critics of markets we consider. Finally, chapter 7 briefly relates the issues to the contemporary discussion about markets, including internal markets and vouchers, in education