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UID:/NewsandEvents/Archives/current/newsitem/15996
 /19-March-2026-Computational-Social-Choice-Seminar
 -Patrick-Lederer
DTSTAMP:20260126T104720
SUMMARY:Computational Social Choice Seminar, Patri
 ck Lederer
ATTENDEE;ROLE=Speaker:Patrick Lederer
DTSTART;TZID=Europe/Amsterdam:20260319T150000
LOCATION:Room L2.07, Lab42, Science Park 900, Amst
 erdam
DESCRIPTION:In rank aggregation, the goal is to co
 mbine multiple input rankings into a single output
  ranking. In this paper, we analyze rank aggregati
 on methods, so-called social welfare functions (SW
 Fs), with respect to strategyproofness, which requ
 ires that no agent can misreport his ranking to ob
 tain an output ranking that is closer to his true 
 ranking in terms of the Kemeny distance. As our ma
 in result, we show that no anonymous SWF satisfies
  unanimity and strategyproofness if there are at l
 east four alternatives. This result is proven by S
 AT solving, a computer-aided theorem proving techn
 ique, and verified by Isabelle, a highly trustwort
 hy interactive proof assistant. Moreover, we show 
 by hand that strategyproofness is incompatible wit
 h majority consistency, a variant of Condorcet-con
 sistency for SWFs. Lastly, we demonstrate for two 
 large classes of SWFs that all SWFs within these c
 lasses have a high incentive ratio and are thus se
 verely manipulable. This is joint work with Manuel
  Eberl.
X-ALT-DESC;FMTTYPE=text/html:\n  <p>In rank aggreg
 ation, the goal is to combine multiple input ranki
 ngs into a single output ranking. In this paper, w
 e analyze rank aggregation methods, so-called soci
 al welfare functions (SWFs), with respect to strat
 egyproofness, which requires that no agent can mis
 report his ranking to obtain an output ranking tha
 t is closer to his true ranking in terms of the Ke
 meny distance. As our main result, we show that no
  anonymous SWF satisfies unanimity and strategypro
 ofness if there are at least four alternatives. Th
 is result is proven by SAT solving, a computer-aid
 ed theorem proving technique, and verified by Isab
 elle, a highly trustworthy interactive proof assis
 tant. Moreover, we show by hand that strategyproof
 ness is incompatible with majority consistency, a 
 variant of Condorcet-consistency for SWFs. Lastly,
  we demonstrate for two large classes of SWFs that
  all SWFs within these classes have a high incenti
 ve ratio and are thus severely manipulable. This i
 s joint work with Manuel Eberl.</p>\n
URL:https://staff.science.uva.nl/u.endriss/seminar
 /
CONTACT:Ulle Endriss at ulle.endriss at uva.nl
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