On Keynesian Economics and the Economics of Keynesafter fifty years

Axel Leijonhufvud'sOn Keynesian Economics and the Economics of Keynes(1968) definitely belongs to the category of "classic" books. Its message-decentralised economies are prone to large increases in unemployment since communication failures prevent the optimal coordination of private decisions-is by now well understood. In this paper, we argue that even though most commentators correctly identify this message, they overlook two crucial aspects of Leijonhufvud's demonstration. These aspects relate to what the author calls the "aggregative structure" and the "transaction structure" of macro-models. We show that the former type of structure plays a central role in the emergence of unemployment in the "Economics of Keynes", while the latter type of structure explains why unemployment is "involuntary".