Computational Democracy Research Seminar - Coders
Computational Democracy Research Seminar - Coders
October 21
Speaker: Patrick Lederer (University of Amsterdam)
Title: Weighted Kemeny Rules for Aggregating Pairwise Preferences
Abstract: In rank aggregation, the goal is to compute a collective ranking over some alternatives based on the voters' preferences over these alternatives. While the literature commonly assumes that preferences take the form of full rankings, reported preferences are typically much sparser in modern applications such as crowdsourcing. Motivated by this observation, we study rank aggregation under pairwise preferences, where each voter reports only her preferences between pairs of alternatives of her choice. For this setting, we axiomatically characterize the class of weighted Kemeny rules, which generalize the well-known Kemeny rule by assigning weights to voters based on how many comparisons between alternatives they report. Our characterization of these rules relies on a population consistency notion called reinforcement and a novel axiom called balanced local Condorcet consistency. We also characterize two particularly natural weighted Kemeny rules: the standard Kemeny rule, which weights all voters equally, and the normalized Kemeny rule, where weights are inversely proportional to the number of reported comparisons. Finally, we conduct simulations to better understand the differences in the behavior of our rules.
This is joint work with Ulle Endriss
November 4
Speaker: Michael A. Müller (University of Fribourg)
December 16
Speaker: Zsombor Meder (University of Groningen)
October 7
Speaker: Pradeep K. Murukannaiah (TU Delft)
Title: Value-Sensitive Decision Making in Democratic Systems
Abstract: Consider a decision context in which a small subset of alternatives is to be chosen among a large set of alternatives. In such a context, it is typical to elicit and aggregate the stakeholders’ preferences on the alternatives to assist decision making. This approach offers insights on what stakeholders prefer, but not why. In this talk, I argue that the exploration of values underlying preferences is a means to answer the why question. I briefly describe the theory of values, how values can be elicited/estimated from stakeholders, and importantly, how the elicited values can be used in decision making. Finally, I describe the challenges in realizing such a value-sensitive decision-making process, e.g., the appropriate level of abstraction at which to conceptualize values, and avenues for future work.
September 16
Title: Computational Democracy Highlights
Speakers: Ivan Bliznets, Julian Chingoma, Davide Grossi, Feline Lindeboom, Grzesiek Lisowski, Pieter van Vliet
Abstract: We will highlight the results of the latest work on computational aspects of democracy by Bernoulli Institute researchers! Each of the speakers will give a short talk showcasing one of their most important results from the last academic year.
August 26
Speaker: Tomasz Wąs (Oxford)
Title: Method of Equal Shares with Bounded Overspending
Abstract
Pure proportional voting rules can sometimes lead to highly suboptimal outcomes. We introduce the Method of Equal Shares with Bounded Overspending (BOS Equal Shares), a robust variant of the Method of Equal Shares that balances proportionality and efficiency. BOS Equal Shares addresses inefficiencies implied by strict proportionality axioms, yet still provides fairness guarantees, similar to the original Equal Shares. Our extensive empirical analysis shows excellent performance of BOS Equal Shares across several metrics. In the course of the analysis, we also study a fractional variant of the Method of Equal Shares.
Joint work with Giorgos Papasotiropoulos, Zein Pishbin, Oskar Skibski, and Piotr Skowron
June 17
Speaker: Zein Pishbin (Université Paris Dauphine-PSL)
Title
Fairness in the Multi-Secretary Problem
Abstract
In this talk, I will discuss how fairness can be incorporated into the multi-secretary problem, where multiple choices are made over time. The presentation connects online algorithms with voting theory, highlights the limits of standard fairness notions in this setting, and introduces methods supported by theory and experiments.