Robustness among multiwinner voting rules

Robert Bredereck, Piotr Faliszewski, Andrzej Kaczmarczyk, Rolf Niedermeier, Piotr Skowron, Nimrod Talmon

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

We investigate how robust the results of committee elections are with respect 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 might be replaced, or (2) it is possible that the whole committee will be replaced. We also show that the problem of computing the smallest number of swaps that lead to changing the election outcome is typically NP-hard, but there are natural FPT algorithms. Finally, for a number of rules we assess experimentally the average number of random swaps necessary to change the election result.

Original languageEnglish
Article number103403
JournalArtificial Intelligence
Volume290
DOIs
StatePublished - 1 Jan 2021

Keywords

  • Committee scoring rules
  • Computational complexity
  • Computational social choice
  • Copeland
  • Parameterized complexity
  • Robustness level
  • Robustness radius
  • STV
  • Winner determination

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