30 May 2022, Computational Social Choice Seminar, Maaike Los

Abstract

Participatory budgeting is a way to allow citizens to have a say in deciding how to spend public funds. It is a generalisation of multi-winner voting, where a committee is to be elected based on the preferences of multiple voters. An important topic in both multi-winner voting and participatory budgeting is fairness of committees or bundles. One way of expressing fairness and increasing the influence of minorities in a participatory budgeting project or multi-winner election, is requiring proportionality of a voting rule. But what is proportionality? Proportionality, although somewhat intuitive, is a complex concept, and can be defined in many different ways. We bring more structure in the landscape of proportionality axioms, and show the existence or non-existence of logical relations between different axioms. Furthermore, we investigate the axiomatic properties of known proportionality-driven rules such as Phragmén and Rule X, and we systematically identify which axioms are satisfied by which voting rules, both in the multi-winner voting and the participatory budgeting setting.

For more information on the Computational Social Choice Seminar, please consult https://staff.science.uva.nl/u.endriss/seminar/.