Beyond Plurality: Truth-Bias in Binary Scoring Rules

It is well known that standard game-theoretic approaches to voting mechanisms lead to a multitude of Nash Equilibria (NE), many of which are counter-intuitive. We focus on truth-biased voters, a model recently proposed to avoid such issues. The model introduces an incentive for voters to be truthful when their vote is not pivotal. This is a powerful refinement, and recent simulations reveal that the surviving equilibria tend to have desirable properties. However, truth-bias has been studied only within the context of plurality elections, which is an extreme example of k-approval rules with k = 1. We undertake an equilibrium analysis of the complete range of k-approval rules (except veto).