When is voting optimal?

We consider a superior decision rule for making collective choices. In our framework, the optimal decision rule depends simply on the decision makers' posterior probabilities of a particular state of nature. In contrast to voting schemes, there is no need to force the decision makers to provide dichotomous information nor to estimate the different abilities of the various decision makers. An important insight is that voting is generally not an efficient way to make collective choices. The purpose of the paper is to shed light on the relationship between the optimal decision rule and voting mechanisms. We derive the conditions under which the optimal decision rule is equivalent to a well-known voting procedure (weighted supermajority, weighted majority, and simple majority) and show that these conditions are very stringent. More general voting procedures that, for example, allow for abstentions, are also considered, and we show that the conditions for reaching the optimal collective choice are still very stringent.