Participatory Budgeting with Project Groups
This work addresses the problem of making participatory budgeting more inclusive for municipalities by allowing for thematic and geographical project groupings with individual budget limits.
This paper generalizes participatory budgeting (PB) by introducing project groups, each with its own budget limit, in addition to a global budget. The authors investigate the computational complexity of maximizing voter satisfaction under these constraints, finding the problem generally intractable but providing efficient exact algorithms for special cases and efficient approximation algorithms.
We study a generalization of the standard approval-based model of participatory budgeting (PB), in which voters are providing approval ballots over a set of predefined projects and -- in addition to a global budget limit, there are several groupings of the projects, each group with its own budget limit. We study the computational complexity of identifying project bundles that maximize voter satisfaction while respecting all budget limits. We show that the problem is generally intractable and describe efficient exact algorithms for several special cases, including instances with only few groups and instances where the group structure is close to be hierarchical, as well as efficient approximation algorithms. Our results could allow, e.g., municipalities to hold richer PB processes that are thematically and geographically inclusive.