False Name Manipulations in Weighted Voting Games: Susceptibility of Power Indices

The splitting of weights into smaller sizes by agents in a weighted voting game and the distribution of the new weights among several false identities with the intent of payoff or power increase in a new game consisting of the original agents as well as the false identities is called false name manipulation. In this paper, we study false name manipulations in weighted voting games focusing on the power indices used in evaluating agents’ payoff in such games. We evaluate the susceptibility to false name manipulations in weighted voting games of the following power indices, namely, Shapley-Shubik, Banzhaf and Deegan-Packel indices when an agent splits into several false identities. Our experimental results suggest that the three power indices are susceptible to false name manipulations when an agent splits into several false identities. However, the Deegan-Packel power index is more susceptible than Shapley-Shubik and Banzhaf indices. General Terms: Algorithms, Economics, Theory