Truthful Aggregation of Budget Proposals

30^th October 2019, 13:00
Nicos Protopapas
University of Liverpool

Abstract

The authors consider a participatory budget problem, where each voter submits a proposal on how to divide a single divisible source among several alternatives (for example public projects) and this proposal should be aggregated into a single division. Voters have a single most preferred division and suffer a disutility equal to the ?1 distance of their most preferred division and the aggregated division. They provide a broad class of mechanisms that are incentive-compatible by generalizing the generalized median rules for single-peaked preferences. They introduce a mechanism from this class that is proportional, in the sense that when voters are single-minded (assign the whole budget to only one alternative) the fraction of the budget assigned to each alternative is equal to the proportion of voters who favor that alternative. They also show that there is a unique Pareto-optimal mechanism in this class, suggesting an inherent tradeoff between Pareto optimality and proportionality.

Authors: Rupert Freeman, David Pennock, Dominik Peters, Jennifer Wortman Vaughan
Appeared at EC '19.