A Model of Expertise

TLDR

Experts are biased and may pull the decision maker in different directions, and a single expert often withholds substantial information. The study examines whether sequential consultation of two experts improves outcomes compared to a single expert in a model where perfectly informed experts advise a decision maker affecting all welfare. The analysis finds no perfect Bayesian equilibrium with full revelation; consulting both experts is never beneficial when they share a bias, but always beneficial when they are biased oppositely, potentially inducing full revelation through rebuttal debates.

Abstract

We study a model in which perfectly informed experts offer advice to a decision maker whose actions affect the welfare of all. Experts are biased and thus may wish to pull the decision maker in different directions and to different degrees. When the decision maker consults only a single expert, the expert withholds substantial information from the decision maker. We ask whether this situation is improved by having the decision maker sequentially consult two experts. We first show that there is no perfect Bayesian equilibrium in which full revelation occurs. When both experts are biased in the same direction, it is never beneficial to consult both. In contrast, when experts are biased in opposite directions, it is always beneficial to consult both. Indeed, in this case full revelation may be induced in an extended debate by introducing the possibility of rebuttal.