A Relation-algebraic Approach to Simple Games

Simple games are a powerful tool to analyze decision-making and coalition formation in social and political life. In this paper, we present relation-algebraic models of simple games and develop relational algorithms for solving some basic problems of them. In particular, we test certain fundamental properties of simple games (being monotone, proper, respectively strong) and compute specific players (dummies, dictators, vetoers, null players) and coalitions (minimal winning coalitions and vulnerable winning coalitions). We also apply relation-algebra to determine central and dominant players, swingers and power indices (the Banzhaf, Holler-Packel and Deegan-Packel indices). This leads to relation-algebraic specifications, which can be executed with the help of the BDD-based tool RelView after a simple translation into the tool's programming language. In order to demonstrate the visualization facilities of RelView we consider an example of the Catalonian Parliament after the 2003 election.relation algebra; RelView; simple game; winning coalition; swinger; dominant player; central player; power index

A relation-algebraic approach to simple games

Simple games are a powerful tool to analyze decision - making and coalition formation in social and political life. In this paper, we present relation-algebraic models of simple games and develop relational specifications for solving some basic problems of them. In particular, we test certain fundamental properties of simple games and compute specific players and coalitions. We also apply relation algebra to determine power indices. This leads to relation-algebraic specifications, which can be evaluated with the help of the BDD-based tool RelView after a simple translation into the tool's programming language. In order to demonstrate the visualization facilities of RelView, we consider an example of the Catalonian Parliament after the 2003 election.Relation algebra ; RelView ; simple game ; winning coalition ; swinger ; dominant player ; central player ; power index

Two new power indices based on winning coalitions

Deegan and Packel (1979) and Holler (1982) proposed two power indices for simple games: the Deegan–Packel index and the Public Good Index. In the definition of these indices, only minimal winning coalitions are taken into account. Using similar arguments, we define two new power indices. These new indices are defined taking into account only those winning coalitions that do not contain null players. The results obtained with the different power indices are compared by means of two real-world examples taken from the political field

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

Power indices and minimal winning coalitions for simple games in partition function form

We propose a generalization of simple games to partition function form games based on a monotonicity property that we define in this context. This property allows us to properly speak about minimal winning embedded coalitions. We propose and characterize two power indices based on such coalitions. Finally, the new indices are used to study the distribution of power in the Parliament of Andalusia that emerged after the elections of March 22, 2015

The essential coalitions index in games with restricted cooperation

We propose a new power index, which we call the essential coalitions index. Within the field of power indices, the new measure extends the Deegan-Packel power index to situations with restricted cooperation. In general, the class of games we study are not simple; with this in mind, we will introduce the essential coalitions as an analogue to the minimal winning coalitions of a simple game, since they generalize some relevant properties. We will first define the new index in terms of three reasonable assumptions, with a similar flavor to those used for the Deegan-Packel index; then, we will formally characterize the index. Finally, through numeric examples, we compare the essential coalitions index to the probabilistic Deegan-Packel index. We see that, in the latter's domain, the two indices only differ by a constant factor. Moreover, the new index is fit to analyze power in the formation of stable coalitions to run a government or a company board

A relation-algebraic approach to simple games

International audienceSimple games are a powerful tool to analyze decision - making and coalition formation in social and political life. In this paper, we present relation-algebraic models of simple games and develop relational specifications for solving some basic problems of them. In particular, we test certain fundamental properties of simple games and compute specific players and coalitions. We also apply relation algebra to determine power indices. This leads to relation-algebraic specifications, which can be evaluated with the help of the BDD-based tool RelView after a simple translation into the tool's programming language. In order to demonstrate the visualization facilities of RelView, we consider an example of the Catalonian Parliament after the 2003 election

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

A new Deegan-Packel inspired power index in games with restricted cooperation

Treballs Finals del Màster d'Economia, Facultat d'Economia i Empresa, Universitat de Barcelona. Curs: 2023-2024, Tutor: Mikel Álvarez MozosWe propose a new power index, which we call the essential coalitions index. The new index is fit to analyze influence in the formation of stable coalitions to run a government or a company board. Within the field of power indices, it extends the Deegan-Packel power index to situations with restricted cooperation; more specifically, to the class of games introduced by Amer and Carreras in [2]. In general, these are not simple games. We will use the essential coalitions as an analogue to the minimal winning coalitions of a simple game, since they generalize some relevant properties. Similarly to the index that inspires it, we will first define the new index in terms of three reasonable assumptions, resembling those used in [5] for the Deegan-Packel index. Then, we formally characterize the index, using suitable modifications of the properties introduced in [2] to characterize the Shapley value in restricted games. Finally, through numeric examples, we compare the essential coalitions index to the similarly inspired, albeit more constrained, probabilístic Deegan-Packel index. We will see that, in the latter’s domain, the two indices only differ in their normalization

Using the multilinear extension to study some probabilistic power indices

The final publication is available at Springer via http://dx.doi.org/10.1007/s10726-016-9514-6We consider binary voting systems modeled by a simple game, in which voters vote independently of each other, and the probability distribution over coalitions is known. The Owen’s multilinear extension of the simple game is used to improve the use and the computation of three indices defined in this model: the decisiveness index, which is an extension of the Banzhaf index, the success index, which is an extension of the Rae index, and the luckiness index. This approach leads us to prove new properties and inter-relations between these indices. In particular it is proved that the ordinal equivalence between success and decisiveness indices is achieved in any game if and only if the probability distribution is anonymous. In the anonymous case, the egalitarianism of the three indices is compared, and it is also proved that, for these distributions, decisiveness and success indices respect the strength of the seats, whereas luckiness reverses this order.Peer ReviewedPostprint (author's final draft