Macro-economische fluctuaties. Nieuw-klassieke en nieuw-Keynesiaanse theorieën

This paper discusses recent developments in the theories about macro-economic fluctuations. We start with a review of some important empirical regularities. The New Classical economists interpret the macro-economic fluctuations as responses to unanticipated monetary and persistent real shocks that are transmitted through expectations and the (intertemporal) substitution of activities in response to change in relative prices. A stabilisation policy is undesirable because fluctuations reflect the optimal responses of the private sector to shocks. Transparent and credible policy rules are necessary to prevent that the public sector becomes a source of instability. The New Keynesian economists focus their attention primarily on nominal shocks and the transmission of these shocks through markets characterised by imperfect competition and imperfect information. Fluctuations are caused by nominal shocks because nominal rigidities in combination with real rigidities prevent an immediate full adjustment, as a consequence a stabilisation policy can improve welfare.