ASSESSMENT OF VOTING SITUATIONS: THE PROBABILISTIC FOUNDATIONS

In this paper we revise the probabilistic foundations of the theory of the measurement of 'voting power' either as success or decisiveness. For an assessment of these features two inputs are claimed to be necessary: the voting procedure and the voters' behavior. We propose a simple model in which the voters' behavior is summarized by a probability distribution over all vote configurations. This basic model, at once simpler and more general that other probabilistic models, provides a clear conceptual common basis to reinterpret coherently from a unified point of view di.erent power indices and some related game theoretic notions, as well as a wider perspective for a dispassionate assessment of the power indices themselves, their merits and their limitations.Voting rules, voting power, decisiveness, success, power indices

Game theory

game theory

The Impact of Council’s Internal Decision-Making Rules on the Future EU

This paper deals with the voting rules in the EU Council. Both internal and external impact of the voting rules are evaluated. Internal impact affects the distribution of power among the member states and external impact affects power relations between the main decision-making bodies in the EU. One of the main lessons of the analysis is clearly to explain why the design of Council voting rules has required so much bargaining and cumbersome marathon negotiations.European integration, Council of Ministers, power

A Smooth Transition from Powerlessness to Absolute Power

We study the phase transition of the coalitional manipulation problem for generalized scoring rules. Previously it has been shown that, under some conditions on the distribution of votes, if the number of manipulators is $o(\sqrt{n})$, where $n$ is the number of voters, then the probability that a random profile is manipulable by the coalition goes to zero as the number of voters goes to infinity, whereas if the number of manipulators is $\omega(\sqrt{n})$, then the probability that a random profile is manipulable goes to one. Here we consider the critical window, where a coalition has size $c\sqrt{n}$, and we show that as $c$ goes from zero to infinity, the limiting probability that a random profile is manipulable goes from zero to one in a smooth fashion, i.e., there is a smooth phase transition between the two regimes. This result analytically validates recent empirical results, and suggests that deciding the coalitional manipulation problem may be of limited computational hardness in practice.Comment: 22 pages; v2 contains minor changes and corrections; v3 contains minor changes after comments of reviewer

Power in the Design of Constitutional Rules

This paper examines different ways of measuring power and the use of these measures in the context of the European Union. The paper deals with classical power indices of co-operative games and more recent non-cooperative a priori measures. Special emphasis of the paper is in inter-institutional balance of power, Nice reforms and eastern enlargement.

Proposal Rights and Political Power

In a canonical model of sequential collective bargaining over a divisible good we show that equilibrium expected payoffs are not restricted by players’ voting rights or their impatience. For all monotonic voting rules and discount factors, and for all divisions of the good among players, there exists a stationary proposal-making rule such that this division represents players’ expected payoffs in a Stationary Subgame Perfect Nash equilibrium in pure strategies. The result attests to the significance of proposal rights in determining political power in collective deliberations.Power, Proposal Rights, Voting Rights.

On stratified sampling for estimating coalitional values

This paper addresses two sampling methodologies to respectively estimate the Owen value and the Banzhaf–Owen value for TU-games with a priori unions. Both proposals are based on stratified sampling on the set of those coalitions that are compatible with the system of unions according to their cardinalities. These sampling methodologies are analysed in terms of the theoretical properties and of the establishment of bounds for the absolute error from a statistical point of view. Finally, we evaluate the performance of these tools on several real well-known examples in the literatureThe author acknowledges the financial support of Ministerio de Economía y Competitividad of the Spanish government under grants MTM2017-87197-C3-2-P and PID2021-124030NB-C32, and of Xunta de Galicia through the ERDF (Grupos de Referencia Competitiva) ED431C 2021/24. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.S

Does Implicit Voting Matter? Coalitional Bargaining in EU the Legislative Process

This paper theorises how decision-makers in the EU legislative process reach consensual decisions and in which policy direction through a mechanism of “implicit voting”. I introduce spatial model coalitional bargaining using a utility function that incorporates decision-maker considerations of the policy gains they expect to obtain for an outcome and the policy concessions they will need to give to other decision-makers so as to have this outcome accepted. The model predicts the formation of a compact coalition where the differences among the distances between each decision-maker position and the coalitional position are less pronounced than in competing alternative coalitions. This coalition will be able to implement this policy position as the outcome of the legislative process. The empirical evaluation of the model with DEU for 44 proposals and 111 issues of EU legislative process shows that the compact coalition offers a good prediction of how consensus in arrived at in the EU, suggesting that implicit voting explains well how EU decisional actors make consensual decisions and the direction this consensus takes

Split Cycle: A New Condorcet Consistent Voting Method Independent of Clones and Immune to Spoilers

We propose a Condorcet consistent voting method that we call Split Cycle. Split Cycle belongs to the small family of known voting methods that significantly narrow the choice of winners in the presence of majority cycles while also satisfying independence of clones. In this family, only Split Cycle satisfies a new criterion we call immunity to spoilers, which concerns adding candidates to elections, as well as the known criteria of positive involvement and negative involvement, which concern adding voters to elections. Thus, in contrast to other clone-independent methods, Split Cycle mitigates both "spoiler effects" and "strong no show paradoxes."Comment: 71 pages, 15 figures. Added a new explanation of Split Cycle in Section 1, updated the caption to Figure 2, the discussion in Section 3.3, and Remark 4.11, and strengthened Proposition 6.20 to Theorem 6.20 to cover single-voter resolvability in addition to asymptotic resolvability. Thanks to Nicolaus Tideman for helpful discussio

Power Indices and Minimal Winning Coalitions in Simple Games with Externalities

We propose a generalization of simple games to sit uations with coalitional externalities. The main novelty of our generalization is a monotonicity property that we define for games in partition function form. This property allows us to properly speak about minimal winning embedded coalitions. We propose and characterize two power indices based on these kind of coalitions. We provide methods based on the multilinear extension of the game to compute the indices. Finally, the new indices are used to study the distribution of power in the current Parliament of Andalusia