Voting Power in the European Union Council under the Nice rules

The purpose of this paper is to compute the Banzhaf power index for weighted voting games as well as weighted double and triple majority games. We calculate the Banzhaf index in an exact way by generating functions, with a signi...cant decrease of the computational complexity. Moreover, the Banzhaf indices are calculated for the decision rules approved in the Nice summit meeting, which will be used in the European Union enlarged to 27 countries. Finally, we show that the triple majority systems adopted are equivalent to weighted simple or double majority games, because the required population quota to approve a decision does not changes the power of the countries.