Probabilistic power indices for voting rules with abstention

In this paper, we introduce eight power indices that admit a probabilistic interpretation for voting rules with abstention or with three levels of approval in the input, briefly (3, 2) games. We analyze the analogies and discrepancies between standard known indices for simple games and the proposed extensions for this more general context. A remarkable difference is that for (3, 2) games the proposed extensions of the Banzhaf index, Coleman index to prevent action and Coleman index to initiate action become non-proportional notions, contrarily to what succeeds for simple games. We conclude the work by providing procedures based on generating functions for weighted (3, 2) games, and extensible to (j,k) games, to efficiently compute them.

► Introduces several new power indices for (3, 2) games. ► Considers several notions of success, decisiveness and luckiness for (3, 2) games. ► Relates probabilistic power indices and standard power indices for (3, 2) games. ► Proposes a method to compute power indices for weighted (3, 2) games.