Quantitative evaluation of veto power

The decisiveness index and the loose protectionism index for a single player have been introduced, starting from the decisiveness and the loose protectionism indices for a collective decisionmaking mechanism defined by Carreras. Attention was mainly focused on the latter index, being proposed as a quantitative measure of the power of veto of each agent. According to this index, a veto player has veto power equal to one, while each other player has a fractional power according to her/his likelihood of blocking a given proposal. Such an index coincides with the expected payoff at the Bayesian equilibrium of a suitable Bayesian game, which illustrates the non-cooperative point of view of a decision-making mechanism.