Optimal voting schemes with costly information acquisition

Alex Gershkov, Balázs Szentes*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

66 Scopus citations


A group of individuals with identical preferences must make a decision under uncertainty about which decision is best. Before the decision is made, each agent can privately acquire a costly and imperfect signal. We discuss how to design a mechanism for eliciting and aggregating the collected information so as to maximize ex-ante social welfare. We first show that, of all mechanisms, a sequential one is optimal and works as follows. At random, one agent at a time is selected to acquire information and report the resulting signal. Agents are informed of neither their position in the sequence nor of other reports. Acquiring information when called upon and reporting truthfully is an equilibrium. We next characterize the ex-ante optimal scheme among all ex-post efficient mechanisms. In this mechanism, a decision is made when the precision of the posterior exceeds a cut-off that decreases with each additional report. The restriction to ex-post efficiency is shown to be without loss when the available signals are sufficiently imprecise. On the other hand, ex-post efficient mechanisms are shown to be suboptimal when the cost of information acquisition is sufficiently small.

Original languageAmerican English
Pages (from-to)36-68
Number of pages33
JournalJournal of Economic Theory
Issue number1
StatePublished - Jan 2009
Externally publishedYes


  • Information aggregation
  • Voting


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