The limits of expert credibility

Jesse Shapiro has a pretty great working paper out: On the Limits of Expert Credibility: Theory and an Application to Climate Change
Abstract: A neutral expert sends an informative message to an uninformed voter. An interested party can pay a cost to replace the expert’s message with its own. The more informed is the expert, the greater is the interested party’s incentive to replace the expert’s message. In equilibrium, making the expert more informed has no effect on the voter’s beliefs and strictly reduces social welfare. The model thus implies an endogenous limit on how credible a purported expert can be. I apply the model to public skepticism about climate change.
The explanation of the intuition behind the model is particularly great:
The intuition for the result is simple. In equilibrium there must be some chance the message is from the expert or the voter would ignore it entirely. Therefore any equilibrium must involve mixing on the part of the informed parties. As a result, the informed parties must be indifferent to hiring an advocate. At the point of indifference, the cost of hiring an advocate must equal the benefit. The benefit to hiring an advocate is proportional to the credibility the voter assigns to the message. The credibility of the message is therefore pinned down, not by the information of the expert, but by the cost of hiring an advocate. The model thus implies an endogenous limit on how informed the voter can be, determined entirely by the market for credentialed advocates. Improved expert information makes society worse off, because it has no impact on voter information and results in greater use of costly advocates.
...as is the specific explanation of results as they apply to the climate change debate:
I apply the model to the climate change debate. As I show in the paper, each side of the debate wields credentialed, credible-sounding experts. Each side accuses the other of exaggerating or falsifying evidence to suit its agenda. It is difficult for the public at large to independently review the scientific evidence on climate change or determine who speaks for the scientific community. The model predicts that under such circumstances the public’s belief will not converge to the scientific consensus. Consistent with this prediction, I show that even highly educated survey respondents express persistent (and growing) skepticism both about climate change itself and about the strength of the scientific consensus.

1 comment: