Monetary Policy, Determinacy, and the Natural Rate Hypothesis

Imposing the natural rate hypothesis (NRH) can dramatically alter the determinacy bounds on monetary policy by closing the output gap in the long run. I show that the hypothesis eliminates any role for the output gap in determinacy and renders the conditions for determinacy identical for all conforming supply equations. Specializing further to IS demand, determinacy depends only on the parameters in the interest rate rule and a pure forward or backward-looking inflation target is inconsistent with determinacy. Monetary policy that embodies the Taylor principle with respect to contemporaneous inflation delivers a determinate equilibrium in all models that satisfy the NRH.Time Series,Natural rate hypothesis; Phillips curve; Taylor Principle

Sticky Information and Determinacy

The infinite-dimensional sticky-information Phillips curve is cast as a finite-dimensional timevarying system of difference equations in order to directly assess determinacy in the model with demand given by the forward-looking IS equation and monetary policy by an interest rate rule. An equivalence to the model without lagged expectations holds (albeit tenuously) for the particular specification and a common truncation method produces spurious determinacy.Determinacy, Taylor rule, Sticky Information, Time-Varying Difference Equations

Solving Linear Rational Expectations Models with Lagged Expectations Quickly and Easily

A solution method is derived in this paper for solving a system of linear rationalexpectations equation with lagged expectations (e.g., models incorporating sticky information) using the method of undetermined coefficients for the infinite MA representation. The method applies a combination of a Generalized Schur Decomposition familiar elsewhere in the literature and a simple system of linear equations when lagged expectations are present to the infinite MA representation. Execution is faster, applicability more general, and use more straightforward than with existing algorithms. Current methods of truncating lagged expectations are shown to not generally be innocuous and the use of such methods are rendered obsolete by the tremendous gains in computational efficiency of the method here which allows for a solution to floating-point accuracy in a fraction of the time required by standard methods. The associated computational application of the method provides impulse responses to anticipated and unanticipated innovations, simulations, and frequency-domain and simulated moments.Lagged expectations; linear rational expectations models; block tridiagonal; Generalized Schur Form; QZ decomposition; LAPACK

The Natural Rate Hypothesis and Real Determinacy

The uniqueness of bounded local equilibria under interest rate rules is analyzed in a model with sticky information `a la Mankiw and Reis (2002). The main results are tighter bounds on monetary policy than in sticky-price models, irrelevance of the degree of output-gap targeting for determinacy, independence of determinacy regions from parameters outside the interest-rate rule, and equivalence between real determinacy in models satisfying the natural rate hypothesis and nominal determinacy in the associated full-information, flex-price equivalent. The analysis follows from boundedness considerations on the nonautonomous recursion that describe the MA(¥) representation of variables’ reaction to endogenous fluctuations.Nonautonomous difference equations; Indeterminacy; Taylor rule; Sticky information; Sticky prices

Existence and Uniqueness of Perturbation Solutions to DSGE Models

We prove that standard regularity and saddle stability assumptions for linear approximations are sufficient to guarantee the existence of a unique solution for all undetermined coefficients of nonlinear perturbations of arbitrary order to discrete time DSGE models. We derive the perturbation using a matrix calculus that preserves linear algebraic structures to arbitrary orders of derivatives, enabling the direct application of theorems from matrix analysis to prove our main result. As a consequence, we provide insight into several invertibility assumptions from linear solution methods, prove that the local solution is independent of terms first order in the perturbation parameter, and relax the assumptions needed for the local existence theorem of perturbation solutions.Perturbation, matrix calculus, DSGE, solution methods, Bézout theorem; Sylvester equations

Solving DSGE Models with a Nonlinear Moving Average

We introduce a nonlinear infinite moving average as an alternative to the standard state-space policy function for solving nonlinear DSGE models. Perturbation of the nonlinear moving average policy function provides a direct mapping from a history of innovations to endogenous variables, decomposes the contributions from individual orders of uncertainty and nonlinearity, and enables familiar impulse response analysis in nonlinear settings. When the linear approximation is saddle stable and free of unit roots, higher order terms are likewise saddle stable and first order corrections for uncertainty are zero. We derive the third order approximation explicitly and examine the accuracy of the method using Euler equation tests.Perturbation, nonlinear impulse response, DSGE, solution methods

Risky LinearApproximations

I construct risk-corrected approximations of the policy functions of DSGEmodels around the stochastic steady state and ergodic mean that are linear in the state variables. The resulting approximations are uniformly more accurate than standard linear approximations and capture the dynamics of asset pricing variables such as the expected risk premium missed by standard linear approximations. The algorithm is fast and reliable, requiring only the solution of linear equations using standard perturbation output. I examine the joint macroeconomic and asset pricing implications of a real business cycle model with stochastic trends and recursive preferences. The method is able to estimate risk aversion under these preferences using the Kalman filter, where a standard linear approximation provides no information and alternative methods require computationally intensive particle filters subject to sampling variation

Monetary Policy, Determinacy, and the Natural Rate Hypothesis

Imposing the natural rate hypothesis (NRH) can dramatically alter the determinacy bounds on monetary policy by closing the output gap in the long run. I show that the hypothesis eliminates any role for the output gap in determinacy and renders the conditions for determinacy identical for all conforming supply equations. Specializing further to IS demand, determinacy depends only on the parameters in the interest rate rule and a pure forward or backward-looking inflation target is inconsistent with determinacy. Monetary policy that embodies the Taylor principle with respect to contemporaneous inflation delivers a determinate equilibrium in all models that satisfy the NRH

The Natural Rate Hypothesis and Real Determinacy

The uniqueness of bounded local equilibria under interest rate rules is analyzed in a model with sticky information `a la Mankiw and Reis (2002). The main results are tighter bounds on monetary policy than in sticky-price models, irrelevance of the degree of output-gap targeting for determinacy, independence of determinacy regions from parameters outside the interest-rate rule, and equivalence between real determinacy in models satisfying the natural rate hypothesis and nominal determinacy in the associated full-information, flex-price equivalent. The analysis follows from boundedness considerations on the nonautonomous recursion that describe the MA(\infty) representation of variables’ reaction to endogenous fluctuations

Sticky Information and Determinacy

The infinite-dimensional sticky-information Phillips curve is cast as a finite-dimensional timevarying system of difference equations in order to directly assess determinacy in the model with demand given by the forward-looking IS equation and monetary policy by an interest rate rule. An equivalence to the model without lagged expectations holds (albeit tenuously) for the particular specification and a common truncation method produces spurious determinacy