His research is in macroeconomics.  He works on rational expectations, intertemporal models of aggregate economies, or what at the moment are called dynamic stochastic general equilibrium (DSGE) models.  Part of his research involves studying the predictions of DSGE models using vector autoregressions (VARs), unobserved component models, and other methods.  This research motivates his recent teaching on financial frictions in general equilibrium models and employing Bayesian VARs to evaluate monetary and fiscal policy.