---
title: "Fairness in Long-Term Participatory Budgeting"
authors:
  - "Martin Lackner"
  - "Jan Maly"
  - "Simon Rey"
doi: "10.24963/ijcai.2021/42"
url: "https://ijcai.org/proceedings/2021/42"
pdf: "https://ijcai.org/proceedings/2021/0042.pdf"
venue: "Proceedings of the Thirtieth International Joint Conference on Artificial Intelligence"
year: 2021
pages: "299-305"
track: "Main Track"
keywords:
  - "Agent-based and Multi-agent Systems: Computational Social Choice"
  - "Agent-based and Multi-agent Systems: Voting"
---

# Fairness in Long-Term Participatory Budgeting

Martin Lackner, Jan Maly, Simon Rey

*Proceedings of the Thirtieth International Joint Conference on Artificial Intelligence*, pages 299-305. DOI: [10.24963/ijcai.2021/42](https://doi.org/10.24963/ijcai.2021/42)

## Abstract

Participatory Budgeting (PB) processes are usually designed to span several years, with referenda for new budget allocations taking place regularly. This paper presents a first formal framework for long-term PB, based on a sequence of budgeting problems as main input. We introduce a theory of fairness for this setting, focusing on three main concepts that apply to types (groups) of voters:
(i) achieving equal welfare for all types, (ii) minimizing inequality of welfare (as measured by the Gini coefficient), and (iii) achieving equal welfare in the long run.
We investigate under which conditions these criteria can be  satisfied, and analyze the computational complexity of verifying whether they hold.