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A Conditional Defense of Plurality Rule: Generalizing May's Theorem in a Restricted Informational Environment
Author(s) -
Goodin Robert E.,
List Christian
Publication year - 2006
Publication title -
american journal of political science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.347
H-Index - 170
eISSN - 1540-5907
pISSN - 0092-5853
DOI - 10.1111/j.1540-5907.2006.00225.x
Subject(s) - majority rule , argument (complex analysis) , voting , simple (philosophy) , mathematical economics , pairwise comparison , social choice theory , style (visual arts) , chain rule (probability) , computer science , mathematics , political science , econometrics , conditional variance , law , artificial intelligence , epistemology , philosophy , volatility (finance) , autoregressive conditional heteroskedasticity , biochemistry , chemistry , archaeology , politics , history
May's theorem famously shows that, in social decisions between two options, simple majority rule uniquely satisfies four appealing conditions. Although this result is often cited in support of majority rule, it has never been extended beyond decisions based on pairwise comparisons of options. We generalize May's theorem to many‐option decisions where voters each cast one vote. Surprisingly, plurality rule uniquely satisfies May's conditions. This suggests a conditional defense of plurality rule: If a society's balloting procedure collects only a single vote from each voter, then plurality rule is the uniquely compelling electoral procedure. To illustrate the conditional nature of this claim, we also identify a richer informational environment in which approval voting, not plurality rule, is supported by a May‐style argument.