Chapter 6 : The Statistical Approach to the Aggregation Problem

These last two decades many authors have pointed out that the way to develop appropriate microfoundations for macroeconomics is not to be found from the study of individuals in isolation but rests in an essential way on studying the aggregate activity resulting from the interaction between different individuals. An alternative approach to the neoclassicla paradigm based on individual rationality has been developped. The fundamentals of the models remain individual behaviors described by individual characteristics. However, the assumptions formalized at the individual level are very weak so that individual rationality might even be redundant. The major assumptions rely on the whole population and, more precisely, on the distribution of agents' characteristics. The purpose of this paper is to give an overview of this approach that we call the "statistical approach" and to present it in an unified framework with the hope that its assumptions will be more systematically used in macroeconomic models.