Séminaires LEMMA

"A theory of social ranking (with applications) "

Stefano MORETTI (Université Paris-Dauphine et CNRS)

Tuesday, 4 November 2025, 11h-12h

Lemma - 4 rue Blaise Desgoffe, 75006 Paris. Salle Maurice Desplas

Abstract : Seemingly unrelated situations, such as team sports, evaluating researchers, argumentation theory, explainable AI, and others, are characterized by a common problem: finding adequate solutions for ranking individuals or elements based on their performance in different groups or coalitions. Recent studies have examined this problem from a theoretical perspective using an axiomatic approach, introducing alternative fundamental properties that a social ranking solution should satisfy to properly convert a coalitional ranking into an individual one. In this seminar, I will focus on a particular solution, called lexicographic excellence, which aims to reward elements that appear frequently in the best coalitions. I’ll present some of its recently studied properties and axiomatic characterizations, and I’ll briefly introduce one of its applications to feature selection in ML models.

References:

Aleandri, M., Fritz, F., Moretti, S. Desirability and social ranking. Soc Choice Welf (2025). https://doi.org/10.1007/s00355-025-01590-1

Bernardi, G., Lucchetti, R. & Moretti, S. Ranking objects from a preference relation over their subsets. Soc Choice Welf 52, 589–606 (2019).https://doi.org/10.1007/s00355-018-1161-1

Gourvès, L., Moretti, S., Tamby, S. (2025). Social Ranking for Feature Selection. In Proceedings of the 24th International Conference on Autonomous Agents and Multiagent Systems (pp. 2547-2549). https://ifaamas.csc.liv.ac.uk/Proceedings/aamas2025/pdfs/p2547.pdf

Suzuki, T., Horita, M. Consistent social ranking solutions. Soc Choice Welf 62, 549–569 (2024). https://doi.org/10.1007/s00355-023-01502-1

"Ideology and Information Cascades: Evidence from French Politicians' Tweets "

Margherita COMOLA (Université Paris-Saclay), joint with S. Shabayek