The Importance of Expertise in Group Decisions

Abstract

Prior to a collective binary choice, members of a group receive binary signals correlated with the better option. Expanding membership may provide no benefit, but expertise is everywhere beneficial. If the group ignores any statistical dependence among the signals, as through majority vote, an expert may perform better than the group. If the group accounts for dependence, a relatively expert member puts an upper bound on the probability of a false belief. The bound holds for any group size and signal distribution. Furthermore, a population investing in expertise is better off cultivating a small mass of elites than adopting an egalitarian policy.