Rational Expectations in the Aggregate

This paper investigates the relationship between the way rational expectations is employed in practice and the argument initially put forth to justify its use. In practice, rational expectations has meant that the expectations of each agent taken separately is consistent with the predictions of the theory. This is different than the argument frequently used by proponents of rational expectations that, on an aggregate level, expectations should be consistent with the theory. The primary findings are that standard and aggregate rational expectations typically yield systematically different equilibria and that the size of the difference depends positively on the degree of synergism. Copyright 1989 by Oxford University Press.