Welfare vs. Representation in Participatory Budgeting

Participatory budgeting (PB) is a democratic process for allocating funds to projects based on the votes of members of the community. Different rules have been used to aggregate participants’ votes. A recent paper by Lackner and Skowron [12] studied the trade-off between notions of social welfare and representation in the multi-winner voting, which is a special case of participatory budgeting with identical project costs. But there is little understanding of this trade-off in the more general PB setting. This paper provides a theoretical and empirical study of the worst-case guarantees of several common rules to better understand the trade-off between social welfare and representation. We show that many of the guarantees from the multi-winner setting do not generalize to the PB setting, and that the introduction of costs leads to substantially worse guarantees, thereby exacerbating the welfare-representation trade-off. We further study how the requirement of proportionality over voting rules effects the guarantees on social welfare and representation. We study the latter point also empirically, both on real and synthetic datasets. We show that variants of the recently suggested voting rule Rule-X (which satisfies proportionality) do very well in practice both with respect to social welfare and representation.

[1]  Piotr Skowron,et al.  Proportionality Degree of Multiwinner Rules , 2018, EC.

[2]  Dominik Peters,et al.  Proportionality and the Limits of Welfarism , 2020, EC.

[3]  Nimrod Talmon,et al.  Participatory Budgeting with Project Interactions , 2020, IJCAI.

[4]  Kamesh Munagala,et al.  The Core of the Participatory Budgeting Problem , 2016, WINE.

[5]  Kamesh Munagala,et al.  Fair Allocation of Indivisible Public Goods , 2018, EC.

[6]  Stanislaw Szufa,et al.  Participatory Budgeting with Cumulative Votes , 2020, ArXiv.

[7]  Edith Elkind,et al.  Proportional Justified Representation , 2016, AAAI.

[8]  Nimrod Talmon,et al.  Proportionally Representative Participatory Budgeting: Axioms and Algorithms , 2017, AAMAS.

[9]  Anja Röcke,et al.  From Porto Alegre to Europe: Potentials and Limitations of Participatory Budgeting , 2022 .

[10]  John R. Chamberlin,et al.  Representative Deliberations and Representative Decisions: Proportional Representation and the Borda Rule , 1983, American Political Science Review.

[11]  Piotr Faliszewski,et al.  What Do Multiwinner Voting Rules Do? An Experiment Over the Two-Dimensional Euclidean Domain , 2017, AAAI.

[12]  J. Lerner,et al.  Budgeting for Equity: How Can Participatory Budgeting Advance Equity in the United States? , 2016 .

[13]  Dominik Peters,et al.  Price of Fairness in Budget Division and Probabilistic Social Choice , 2020, AAAI.

[14]  Celina Su.  From Porto Alegre to New York City: Participatory Budgeting and Democracy , 2017 .

[15]  Dariusz Stolicki,et al.  Pabulib: A Participatory Budgeting Library , 2020, ArXiv.

[16]  Dominik Peters,et al.  Proportional Participatory Budgeting with Cardinal Utilities , 2020, ArXiv.

[17]  Haris Aziz,et al.  Justified representation in approval-based committee voting , 2014, Social Choice and Welfare.

[18]  Martin Lackner,et al.  Utilitarian welfare and representation guarantees of approval-based multiwinner rules , 2020, Artif. Intell..

[19]  Ashish Goel,et al.  Knapsack Voting for Participatory Budgeting , 2019, ACM Trans. Economics and Comput..