When the number of players is small in a weighted majority voting game, it can occur that one of the players has no influence on the result of the vote, in spite of a strictly positive weight. Such a player is called a “dummy” player in game theory. The purpose of this paper is to...

In this paper we analyze the fairness of the 2007 reform proposal concerning the apportionment of the seats between the regions for the Italian Senate. Theory of power indices is used to compare the actual case with the proposed one. Two scenarios are proposed, senators belonging to the same...

In this paper, we compare five well-known methods of apportionment, the ones by Adams, Dean, Hill, Webster and Jefferson. The criteria used for this comparison is the minimization of a distance between a power vector and a population vector. The power is measured with the well-known Banzhaf...

The purpose of this paper is to present a structural specification of the Shapley- Shubik and Banzhaf power indices in a weighted voting rule. We compare them in term of the cardinality of the sets of power vectors (PV). This is done in different situations where the quota or the number of seats...

This paper analyzes a sequential voting mechanism that eliminates at each round one candidate, until only one of them is left (the winner). The candidates are the voters and they only differ across their skill level. The payoff allocated to the winner depends on the sequence of elimination of...

A well-known result in Social Choice theory is the following: every scoring rule (positional rules) violates Condorcet consistency. A rule is Condorcet consistent when it selects the alternative that is preferred to every other alternative by a majority of individuals. In this paper, we...

According to a given quota q, a candidate a is beaten by another candidate b if at least a proportion of q individuals prefer b to a. The q-Condorcet efficiency of a voting rule is the probability that the rule selects a q-Condorcet winner (q-CW), that is any candidate who is never beaten under...

How can we count and list all the Banzhaf or Shapley-Shubik index of power configurations for a given number of players? There is no formula in the literature that may give the cardinal of such a set, and moreover, even if this formula had existed, there is no formula which gives the...

The spatial analysis of power indices is commonly used in the literature to study the importance of ideological criteria. Our purpose is to show, through the example of some french groupings of local cities, the importance of the geographical situation of the players when considering power...