Jan Maly (University of Amsterdam): "Proportionality in Participatory Budgeting"

Budgeting, i.e., the allocation of money or other sparse resources to specific projects, is one of the key decisions any political body or organisation has to take. Participatory budgeting (PB) was developed in the 1990s as a method for making such decisions in more democratic a way, by putting the selection of projects to be funded to a vote. It has found rapid adoption worldwide, in particular at the municipal level. In recent years, researchers have started to look for voting rules that make the PB process fairer by producing proportional outcomes. So far, the literature has focused on generalising from approval-based multiwinner voting, where we often aim for a proportional distribution of satisfaction amongst voters. However, due to the varying cost of projects, it is unclear how to define satisfaction in PB. In this talk, I will present two ideas for defining proportionality in PB without knowing the exact satisfaction of each voter.