Majority Rule in the Absence of a Majority
52 Pages Posted: 10 Feb 2018
Date Written: January 30, 2018
Which is the best, impartially most plausible consensus view to serve as the basis of democratic group decision when voters disagree? Assuming that the judgement aggregation problem can be framed as a matter of judging a set of binary propositions (“issues”), we develop a multi-issue majoritarian approach based on the criterion of supermajority efficiency (SME). SME reflects the idea that smaller supermajorities must yield to larger supermajorities so as to obtain better supported, more plausible group judgments. As it is based on a partial ordering, SME delivers unique outcomes only in special cases. In general, one needs to make cardinal, not just ordinal, trade-offs between different supermajorities. Hence we axiomatically characterize the class of additive majority rules, whose (generically unique) outcome can be interpreted as the “on balance most plausible” consensus judgement.
Keywords: Judgement Aggregation, Majoritarian, Supermajority, Hyperreal
JEL Classification: D71
Suggested Citation: Suggested Citation