Voting and optimal provision of a public good *

•We study the optimal provision of a public good by dominant-incentive compatible mechanisms.•A simple voting mechanism is optimal among all mechanisms that are dominant-incentive-compatible, deficit-free, and kind.•The optimal voting mechanism outperforms the symmetric pivotal mechanism.

In this paper, we study the optimal provision of a costly public good using an average efficiency criterion. For every fixed cost, we identify a quota mechanism as the optimal mechanism among those that are dominant-incentive-compatible, deficit-free and kind. Moreover, we also consider the asymmetric case and demonstrate that a committee mechanism is optimal for a large class of mechanisms. In particular, this mechanism dominates all VCG (pivotal) mechanisms.