Multiwinner Voting with Possibly Unavailable Candidates

Properties of multiwinner voting rules

The goal of this paper is to propose and study properties of multiwinner voting rules (with a particular focus on rules based in some way on single-winner scoring rules). We consider, e.g., SNTV, Bloc, k-Borda, STV, and several variants of Chamberlin–Courant’s and Monroe’s rules, identify two natural approaches to defining multiwinner rules, and show that many of our rules can be captured by on...

Robustness Among Multiwinner Voting Rules

We investigate how robust are results of committee elections to small changes in the input preference orders, depending on the voting rules used. We find that for typical rules the effect of making a single swap of adjacent candidates in a single preference order is either that (1) at most one committee member can be replaced, or (2) it is possible that the whole committee can be replaced. We a...

Group Fairness in Multiwinner Voting

We study multiwinner voting problems when there is an additional requirement that the selected committee should be fair with respect to attributes such as gender, ethnicity, or political parties. Every setting of an attribute gives rise to a group, and the goal is to ensure that each group is neither over nor under represented in the selected committee. Prior work has largely focused on designi...

Approval voting with endogenous candidates

We present a formal model of political competition under approval voting which allows for endogenous candidate entry. Our analysis yields a number of novel insights. First, we develop a notion of sincere voting behavior under approval voting, called relative sincerity. We then show that the relatively sincere voting behavior is consistent with the strategic calculus of voting. Second, we show t...

Multiwinner Voting: A New Challenge for Social Choice Theory