Participatory Budgeting Project Strength via Candidate Control

2025-05-28

Adaptive Agents and Multi-Agent Systems

AI Summary

This study investigates the computational complexity of manipulating participatory budgeting elections by adding or deleting candidate projects to either ensure a target project’s selection (constructive control) or its exclusion (destructive control). It presents the first systematic analysis of candidate control under prominent voting rules—Phragmén, Equal Shares, and GreedyAV—and introduces a novel perspective that evaluates project strength through the lens of candidate deletions. The theoretical findings reveal that the problem is NP-hard under most rules, yet polynomial-time algorithms exist for GreedyAV and in the unit-cost setting. Experimental results corroborate the efficacy of the proposed approach, offering both theoretical insights and practical tools for assessing the robustness of participatory budgeting outcomes and the relative importance of individual projects.

Technology Category

• Game Theory and Economic Paradigms: Social Choice / Voting
• Knowledge Representation and Reasoning: Computational Complexity of Reasoning
• Constraint Satisfaction and Optimization: Constraint Programming

Application Category

• Economics, Online Markets and Human Computation: Data quality aspects of human-annotated datasets
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Security and Privacy: Large-scale security measurements

Abstract

We study the complexity of candidate control in participatory budgeting elections. The goal of constructive candidate control is to ensure that a given candidate wins by either adding or deleting candidates from the election (in the destructive setting, the goal is to prevent a given candidate from winning). We show that such control problems are NP-hard to solve for many participatory budgeting voting rules, including Phragmén and Equal-Shares, but there are natural cases with polynomial-time algorithms. We also argue that control by deleting candidates is a useful tool for assessing the performance (or, strength) of initially losing projects, and we support this view with experiments on real-life PB instances.

Problem

• Participatory Budgeting
• Candidate Control
• Computational Complexity
• Voting Rules
• Project Selection

Innovation

• Participatory Budgeting
• Candidate Control
• Computational Complexity
• Project Strength
• Voting Rules