Monetary Policy Rules, Learning and Stability: a Survey of the Recent Literature (In French)

This paper presents the literature about econometric learning and its impact on the performances of monetary policy rules in the framework of the new canonical macroeconomic model. Rational expectations which are a building block of the original model can thus be replaced by expectations based on estimation algorithms. The permanent updating of these estimations can be interpreted as a learning proces of the model’s agents. This learning proces induces additional dynamics into the model. The literature in question uses two criteria in order to analyse the ability of monetary policy rules to stabilise the economy: (i) uniqueness of the rational expectations equilibrium in the original model and (ii) stability in regards to learning in the modified model. Taking learning into account enables to detect shortcomings of a rule according to (ii) that would not been seen in a rational expectations model. However, the main message of the surveyed literature is that most of the results found in a rational expectations framework are robust. The paper ends with a discussion on the specific problems met in the introduction of a learning proces in the new canonical model.monetary policy rules – learning – determination - stability

Learning the optimal buffer-stock consumption rule of Carroll

This article questions the rather pessimistic conclusions of Allen et Carroll (2001) about the ability of consumer to learn the optimal buffer-stock based consumption rule. To this aim, we develop an agent based model where alternative learning schemes can be compared in terms of the consumption behaviour that they yield. We show that neither purely adaptive learning, nor social learning based on imitation can ensure satisfactory consumption behaviours. By contrast, if the agents can form adaptive expectations, based on an evolving individual mental model, their behaviour becomes much more interesting in terms of its regularity, and its ability to improve performance (which is as a clear manifestation of learning). Our results indicate that assumptions on bounded rationality, and on adaptive expectations are perfectly compatible with sound and realistic economic behaviour, which, in some cases, can even converge to the optimal solution. This framework may therefore be used to develop macroeconomic models with adaptive dynamics.Consumption decisions; Learning; Expectations; Adaptive behaviour, Computational economics