Fair Group Decisions via Non-deterministic Proportional Consensus

100 Pages Posted: 18 Feb 2021 Last revised: 1 Nov 2023

See all articles by Jobst Heitzig

Jobst Heitzig

Potsdam-Institut für Klimafolgenforschung (PIK); Konrad-Zuse-Zentrum für Informationstechnik - Zuse-Institut Berlin (ZIB)

Forest W. Simmons

Portland Community College

Sara Constantino

Princeton University; Northeastern University

Date Written: May 15, 2022

Abstract

Are there group decision methods which
(i) give everyone, including minorities, an equal share of effective decision power even when voters act strategically,
(ii) promote consensus and equality, rather than polarization and inequality, and
(iii) do not favour the status quo or rely too much on chance?

We describe two non-deterministic group decision methods that meet these criteria, one based on automatic bargaining over lotteries, the other on conditional commitments to approve compromise options. Using theoretical analysis, agent-based simulations and a behavioral experiment, we show that these methods prevent majorities from consistently suppressing minorities, as is the case with deterministic methods, and proponents of the status quo from blocking decisions, as in other consensus-based approaches.

Our simulations show that these methods achieve aggregate welfare comparable to common voting methods, while employing chance judiciously, and that the welfare costs of fairness and consensus are small compared to the inequality costs of majoritarianism. In an incentivized experiment with naive participants, we find that a sizable fraction of participants prefers to use a non-deterministic voting method over Plurality Voting to allocate monetary resources. However, this depends critically on their position within the group. Those in the majority show a strong preference for majoritarian voting methods.

The PDF contains the 29 pages long main article plus 71 pages of Supplementary Information.

Keywords: non-majoritarian group decisions, conditional commitments, fairness, strategic voting

JEL Classification: D71, D72, C78, D82

Suggested Citation

Heitzig, Jobst and Simmons, Forest W. and Constantino, Sara, Fair Group Decisions via Non-deterministic Proportional Consensus (May 15, 2022). Available at SSRN: https://ssrn.com/abstract=3751225 or http://dx.doi.org/10.2139/ssrn.3751225

Jobst Heitzig (Contact Author)

Potsdam-Institut für Klimafolgenforschung (PIK) ( email )

Telegraphenberg A 31
P.O. Box 60 12 03
Potsdam, Brandenburg 14412
Germany
+49 331 288-2692 (Phone)

HOME PAGE: http://www.pik-potsdam.de/members/heitzig

Konrad-Zuse-Zentrum für Informationstechnik - Zuse-Institut Berlin (ZIB)

Takustrasse 7
Berlin, 14195
Germany

Forest W. Simmons

Portland Community College ( email )

United States

Sara Constantino

Princeton University ( email )

Northeastern University ( email )

220 B RP
Boston, MA 02115
United States

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