Participatory Budgeting with Cumulative Votes

TL;DR

This paper introduces new aggregation methods for participatory budgeting using cumulative votes, with one method showing strong proportionality and practical promise based on axiomatic and simulation evaluations.

Contribution

The paper proposes novel cumulative vote-based aggregation methods for participatory budgeting, highlighting a particularly effective method called Minimal Transfers over Costs.

Findings

Minimal Transfers over Costs outperforms existing methods.

The proposed method satisfies strong proportionality.

Computer simulations confirm its desirable behavior.

Abstract

In participatory budgeting we are given a set of projects---each with a cost, an available budget, and a set of voters who in some form express their preferences over the projects. The goal is to select---based on voter preferences---a subset of projects whose total cost does not exceed the budget. We propose several aggregation methods based on the idea of cumulative votes, e.g., for the setting when each voter is given one coin and she specifies how this coin should be split among the projects. We compare our aggregation methods based on (1) axiomatic properties, and (2) computer simulations. We identify one method, Minimal Transfers over Costs, that demonstrates particularly desirable behavior. In particular, it significantly improves on existing methods, satisfies a strong notion of proportionality, and, thus, is promising to be used in practice.