The Price of Justified Representation


  • Edith Elkind University of Oxford
  • Piotr Faliszewski AGH University of Science and Technology
  • Ayumi Igarashi National Institute of Informatics
  • Pasin Manurangsi Google Research
  • Ulrike Schmidt-Kraepelin TU Berlin
  • Warut Suksompong National University of Singapore



Game Theory And Economic Paradigms (GTEP)


In multiwinner approval voting, the goal is to select k-member committees based on voters' approval ballots. A well-studied concept of proportionality in this context is the justified representation (JR) axiom, which demands that no large cohesive group of voters remains unrepresented. However, the JR axiom may conflict with other desiderata, such as coverage (maximizing the number of voters who approve at least one committee member) or social welfare (maximizing the number of approvals obtained by committee members). In this work, we investigate the impact of imposing the JR axiom (as well as the more demanding EJR axiom) on social welfare and coverage. Our approach is threefold: we derive worst-case bounds on the loss of welfare/coverage that is caused by imposing JR, study the computational complexity of finding 'good' committees that provide JR (obtaining a hardness result, an approximation algorithm, and an exact algorithm for one-dimensional preferences), and examine this setting empirically on several synthetic datasets.




How to Cite

Elkind, E., Faliszewski, P., Igarashi, A., Manurangsi, P., Schmidt-Kraepelin, U., & Suksompong, W. (2022). The Price of Justified Representation. Proceedings of the AAAI Conference on Artificial Intelligence, 36(5), 4983-4990.



AAAI Technical Track on Game Theory and Economic Paradigms