Dummy Players and the Quota in Weighted Voting Games
Résumé
In a weighted voting game, each voter has a weight and a proposal is accepted if
the sum of the weights of the voters in favor of that proposal is at least as large as a
certain quota. It is well-known that, in this kind of voting process, it can occur that
the vote of a player has no efect on the outcome of the game; such a player is called
a “dummy” player. This paper studies the role of the quota on the occurrence of
dummy players in weighted voting games. Assuming that every admissible weighted
voting game is equally likely to occur, we compute the probability of having a player
without voting power as a function of the quota for three, four and fve players. It
turns out that this probability is very sensitive to the choice of the quota and can be
very high. The quota values that minimize (or maximize) the likelihood of dummy
players are derived (Some technical details are voluntarily omitted in this version
of our study. These details can be found in the online appendix associated with this
paper at https://bit.ly/2MVVuBW).