Fair Lotteries for Participatory Budgeting (2404.05198v2)
Abstract: In pursuit of participatory budgeting (PB) outcomes with broader fairness guarantees, we initiate the study of lotteries over discrete PB outcomes. As the projects have heterogeneous costs, the amount spent may not be equal ex ante and ex post. To address this, we develop a technique to bound the amount by which the ex-post spend differs from the ex-ante spend -- the property is termed budget balanced up to one project (BB1). With respect to fairness, we take a best-of-both-worlds perspective, seeking outcomes that are both ex-ante and ex-post fair. Towards this goal, we initiate a study of ex-ante fairness properties in PB, including Individual Fair Share (IFS), Unanimous Fair Share (UFS) and their stronger variants, as well as Group Fair Share (GFS). We show several incompatibility results between these ex-ante fairness notions and existing ex-post concepts based on justified representation. One of our main contributions is a randomized algorithm which simultaneously satisfies ex-ante Strong UFS, ex-post full justified representation (FJR) and ex-post BB1 for PB with binary utilities.
- M. Akbarpour and A. Nikzad. Approximate random allocation mechanisms. The Review of Economic Studies, 01 2020. rdz066.
- H. Aziz. A probabilistic approach to voting, allocation, matching, and coalition formation. In J.-F. Laslier, H. Moulin, R. Sanver, and W. S. Zwicker, editors, The Future of Economic Design. Springer Cham, 2019.
- H. Aziz and N. Shah. Participatory budgeting: Models and approaches. In Tamás Rudas and Gábor Péli, editors, Pathways Between Social Science and Computational Social Science: Theories, Methods, and Interpretations, pages 215–236. Springer International Publishing, 2021.
- Justified representation in approval-based committee voting. Social Choice and Welfare, 48(2):461–485, 2017.
- Proportionally representative participatory budgeting: Axioms and algorithms. In Proceedings of the 17th International Conference on Autonomous Agents and Multiagent Systems (AAMAS), pages 23–31, 2018.
- Strategyproof peer selection using randomization, partitioning, and apportionment. Artificial Intelligence, 275:295–309, 2019.
- Best of both worlds: Ex ante and ex post fairness in resource allocation. Operations Research, 2023a. Forthcoming.
- Best of both worlds fairness under entitlements. In Proceedings of the 22nd International Conference on Autonomous Agents and Multiagent Systems (AAMAS), pages 941–948, 2023b.
- Best-of-both-worlds fairness in committee voting. In Proceedings of the 19th Conference on Web and Internet Economics (WINE), page 676, 2023c. Extended version available at https://arxiv.org/abs/2303.03642.
- On best-of-both-worlds fair-share allocations. In Proceedings of the 18th Conference on Web and Internet Economics (WINE), pages 237–255, 2022.
- A. Bogomolnaia and H. Moulin. A new solution to the random assignment problem. Journal of Economic Theory, 100(2):295–328, 2001.
- Collective choice under dichotomous preferences. Journal of Economic Theory, 122(2):165–184, 2005.
- M. Brill and J. Peters. Robust and verifiable proportionality axioms for multiwinner voting. In Proceedings of the 24th ACM Conference on Economics and Computation (EC), page 301, 2023.
- Proportionality in approval-based participatory budgeting. In Proceedings of the 37th AAAI Conference on Artificial Intelligence (AAAI), pages 5524–5531, 2023.
- Group fairness in committee selection. ACM Transactions on Economics and Computation, 8(4):1–18, 2020.
- The price of justified representation. In Proceedings of the 36th AAAI Conference on Artificial Intelligence (AAAI), pages 4983–4990, 2022.
- The core of the participatory budgeting problem. In Proceedings of the 12th International Conference on Web and Internet Economics (WINE), pages 384–399, 2016.
- Breaking the envy cycle: Best-of-both-worlds guarantees for subadditive valuations. CoRR, abs/2304.03706, 2023.
- Dependent rounding and its applications to approximation algorithms. Journal of the ACM, 53(3):324–360, 2006.
- Knapsack voting for participatory budgeting. ACM Transactions on Economics and Computation, 7(2):1–27, 2019.
- In this apportionment lottery, the house always wins. In Proceedings of the 23rd ACM Conference on Economics and Computation (EC), page 562, 2022.
- Best of both worlds: Agents with entitlements. In Proceedings of the 22nd International Conference on Autonomous Agents and Multiagent Systems (AAMAS), pages 564–572, 2023.
- M. Lackner and P. Skowron. Multi-Winner Voting with Approval Preferences. Springer, 2023.
- Proportional budget allocations: Towards a systematization. In Proceedings of the 31st International Joint Conference on Artificial Intelligence (IJCAI), pages 398–404, 2022.
- Approximate core for committee selection via multilinear extension and market clearing. In Proceedings of the 2022 Annual ACM-SIAM Symposium on Discrete Algorithms (SODA), pages 2229–2252, 2022.
- Proportional participatory budgeting with additive utilities. In Proceedings of the 35th Conference on Neural Information Processing Systems (NeurIPS), pages 12726–12737, 2021. Extended version available at https://arxiv.org/abs/2008.13276v2.
- S. Rey and J. Maly. The (computational) social choice take on indivisible participatory budgeting. CoRR, abs/2303.00621, 2023.
- Proportional justified representation. In Proceedings of the 31st AAAI Conference on Artificial Intelligence (AAAI), pages 670–676, 2017.
- M. Suzuki and J. Vollen. Maximum flow is fair: A network flow approach to committee voting. Manuscript, 2024.