Aggregation and Social Choice: A Mean Voter Theorem.

A celebrated result of D. Black (1948) demonstrates the existence of a simple-majority winner when preferences are single-peaked. This paper provides a multidimensional analog of Black's median voter result. The authors provide conditions under which the mean voter's most preferred outcome is unbeatable according to a 64 percent majority rule. The conditions supporting this result represent a significant generalization of A. Caplin and B. Nalebuff (1988). The shift from median voter to mean voter requires a new mathematical approach; the authors introduce to economics a mathematical aggregation theorem due to A. Pr$8Ekopa (1971) and C. Borell (1975). Copyright 1991 by The Econometric Society.