Computing the proportional veto core

03/20/2020

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by   Egor Ianovski, et al.

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Moulin (1981) has argued in favour of electing an alternative by giving each coalition the ability to veto a number of alternatives roughly proportional to the size of the coalition and considering the core of the resulting cooperative game. This core is guaranteed to be non-empty, and offers a large measure of protection for minorities (Kondratev and Nesterov, 2020). However, as is the norm for cooperative game theory the formulation of the concept involves considering all possible coalitions of voters, so the naive algorithm would run in exponential time, limiting the application of the rule to trivial cases only. In this work we present a polynomial time algorithm to compute the proportional veto core.