Deliberation and the Wisdom of CrowdsFranz Dietrich and Kai Spiekermann
16 December 2021
Franz Dietrich (Paris School of Economics & CNRS/CES) and Kai Spiekermann (London School of Economics), 17:15 - 18:45, present their work in the Interdisciplinary Research Seminar of the GRK "Collective Decision-Making”.
This seminar will take place via Zoom. Please register (if you haven’t already) here if you want to attend the seminar. We invite everyone interested to attend!
Abstract
Under the epistemic interpretation of voting, votes express judgments about what is correct, and the aggregation rule aims to generate correct outcomes, using the individual judgments as informational input. Is group deliberation epistemically beneficial, i.e., does it tend to change individual judgments in ways that improve the aggregate outcome? To tackle this notorious question, we construe deliberation as information sharing. That is, each voter bases their judgment on some personal set of evidence items, and during deliberation any voter shares some or all of their evidence with others, so that the evidence sets of voters increase and become more similar. We present a formal model that captures deliberation as information sharing, and use this model to highlight and simulate three voting failures and their potential reduction through deliberation. The first failure is the overrepresentation of widespread evidence: evidence items held by many voters are overrepresented in voting outcomes as compared to evidence items held by few or just one voter. The second failure is the neglect of evidence strength: because of “one man one vote”, each voter has the same impact regardless of the strength of their evidence. The third failure is the neglect of informational complementarities across voters: knowledge that would follow by combining evidence of different voters fails to enter voting outcomes, as it does not enter any voter’s vote. We finally address the relationship to jury theorems.