Online Social Choice and Welfare Seminar: Eric Pacuit, Tuesday 17 February
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Marcus Pivato
Feb 11, 2026, 4:16:30 AM (13 days ago) Feb 11
to social-choice-a...@googlegroups.com, com...@duke.edu
[with apologies for cross-posting]
Dear all,
The next presentation in the Online Social Choice and Welfare Seminar will be next Tuesday (17 February). Here are the details.
Time: 2PM GMT (9AM College Park, 11AM Rio de Janeiro, 2PM London, 3PM Paris, 5PM Istanbul, 7:30PM New Delhi, 11PM Tokyo/Seoul)
Speaker: Eric Pacuit (University of Maryland)
Title: "Characterizations of voting rules based on majority margins"
Abstract. In the context of voting with ranked ballots, an important class of voting rules is the class of margin-based rules (also called pairwise rules). A voting rule is margin-based if whenever two elections generate the same head-to-head margins of victory or loss between candidates, then the voting rule yields the same outcome in both elections. Although this is a mathematically natural invariance property to consider, whether it should be regarded as a normative axiom on voting rules is less clear. In this paper, we address this question for voting rules with any kind of output, whether a set of candidates, a ranking, a probability distribution, etc. We prove that a voting rule is margin-based if and only if it satisfies some axioms with clearer normative content. A key axiom is what we call Preferential Equality, stating that if two voters both rank a candidate x immediately above a candidate y, then either voter switching to rank y immediately above x will have the same effect on the election outcome as if the other voter made the switch, so each voter's preference for y over x is treated equally.
This is joint work with Yifeng Ding and Wes Holliday.
Reminder: On the seminar website you can find the video recordings, slides and supplementary materials for all past presentations, as well as information about future presentations.
-- Dear all,
The next presentation in the Online Social Choice and Welfare Seminar will be next Tuesday (17 February). Here are the details.
Time: 2PM GMT (9AM College Park, 11AM Rio de Janeiro, 2PM London, 3PM Paris, 5PM Istanbul, 7:30PM New Delhi, 11PM Tokyo/Seoul)
Speaker: Eric Pacuit (University of Maryland)
Title: "Characterizations of voting rules based on majority margins"
Abstract. In the context of voting with ranked ballots, an important class of voting rules is the class of margin-based rules (also called pairwise rules). A voting rule is margin-based if whenever two elections generate the same head-to-head margins of victory or loss between candidates, then the voting rule yields the same outcome in both elections. Although this is a mathematically natural invariance property to consider, whether it should be regarded as a normative axiom on voting rules is less clear. In this paper, we address this question for voting rules with any kind of output, whether a set of candidates, a ranking, a probability distribution, etc. We prove that a voting rule is margin-based if and only if it satisfies some axioms with clearer normative content. A key axiom is what we call Preferential Equality, stating that if two voters both rank a candidate x immediately above a candidate y, then either voter switching to rank y immediately above x will have the same effect on the election outcome as if the other voter made the switch, so each voter's preference for y over x is treated equally.
This is joint work with Yifeng Ding and Wes Holliday.
To obtain the Zoom link, please subscribe to the Seminar Mailing List, or contact one of the organisers.
Reminder: On the seminar website you can find the video recordings, slides and supplementary materials for all past presentations, as well as information about future presentations.
Marcus Pivato
Centre d'Économie de la Sorbonne
Centre d'Économie de la Sorbonne
Université Paris 1 Panthéon-Sorbonne
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