# Epistemic selection of costly alternatives: the case of participatory budgeting

## TL;DR

This paper explores how voting rules in participatory budgeting can be evaluated based on their ability to reflect the best possible funding decisions.

## Contribution

The paper introduces the epistemic approach to analyze participatory budgeting rules and identifies limitations of existing methods.

## Key findings

- Commonly studied and used budgeting rules lack epistemic justification as maximum likelihood estimators.
- Welfare-maximizing rules show mixed results in terms of epistemic guarantees.

## Abstract

We initiate the study of voting rules for participatory budgeting using the so-called epistemic approach, where one interprets votes as noisy reflections of some ground truth regarding the objectively best set of projects to fund. Using this approach, we first show that both the most studied rules in the literature and the most widely used rule in practice cannot be justified on epistemic grounds: they cannot be interpreted as maximum likelihood estimators, whatever assumptions we make about the accuracy of voters. Focusing then on welfare-maximising rules, we obtain both positive and negative results regarding epistemic guarantees.