Policy Evaluation and Design for Continuous Time Linear Rational Expectations Models: Some Recent Developments

This paper surveys some recent developments in policy evaluation and design in continuous time linear rational expectations models. Much recent work in macroeconomics and open economy macroeconomics fits into this category. First the continuous time analogue of the discrete time solution method of Blanchard and Kahn is reviewed. Some problems associated with this solution method are then discussed, including non-uniqueness and zero roots. Optimal (but in general time-inconsistent) and time-consistent (but in general suboptimal) solutions are derived to the general linear-quadratic optimal control problem, based on work by Calco, Driffill, Miller and Salmon and the author. A numerical example is solved, involving optimal and time-consistent anti-inflationary policy design in a contract model.