Project Submission Games in Participatory Budgeting

2025-08-13

AI Summary

This paper addresses strategic project submission by proposers in participatory budgeting (and multi-winner elections), introducing the first formal “project submission game”: each proposer selects a subset of projects to maximize the total cost of their funded projects. The study investigates existence conditions, computational complexity of deciding existence, and algorithm design for best responses under pure Nash equilibria (NE). Theoretically, it establishes sufficient conditions for NE existence and proves that deciding NE existence is Σ₂^P-complete—revealing a fundamental tension between mechanism design and equilibrium implementability. Algorithmically, it proposes a polynomial-time best-response algorithm applicable to a broad class of utility structures. By unifying the strategic nature of proposer behavior, this work provides a foundational game-theoretic framework for analyzing and designing robust participatory budgeting mechanisms.

Technology Category

• Game Theory and Economic Paradigms: Mechanism Design
• Multiagent Systems: Mechanism Design
• Reasoning under Uncertainty: Decision/Utility Theory

Application Category

• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems
• Graph Algorithms and Modeling for the Web: Algorithms and analysis for incomplete, noisy, or partially observed Web-related graphs
• Responsible Web: Human-perceived consequences of algorithmic deployment on the web

Abstract

We introduce the framework of project submission games, capturing the behavior of project proposers in participatory budgeting (and multiwinner elections). Here, each proposer submits a subset of project proposals, aiming at maximizing the total cost of those that get funded. We focus on finding conditions under which pure Nash equilibria (NE) exist in our games, and on the complexity of checking whether they exist. We also seek algorithms for computing best responses for the proposers

Problem

• Modeling strategic project proposer behavior in participatory budgeting
• Analyzing existence conditions for pure Nash equilibria
• Investigating computational complexity of equilibrium verification

Innovation

• Introduces project submission games framework
• Analyzes Nash equilibria existence conditions
• Develops best response computation algorithms