A, B, C's (and D'S) for Understanding Vars
49 Pages Posted: 4 May 2005
Date Written: May 2, 2005
The dynamics of a linear (or linearized) dynamic stochastic economic model can be expressed in terms of matrices (A,B,C,D) that define a state space system. An associated state space system (A,K,C, Sigma) determines a vector autoregression for observables available to an econometrician. We review circumstances under which the impulse response of the VAR resembles the impulse response associated with the economic model. We give four examples that illustrate a simple condition for checking whether the mapping from VAR shocks to economic shocks is invertible. The condition applies when there are equal numbers of VAR and economic shocks.
Keywords: VARs , Invertibility, Estimation of Dynamic Equilibrium Models, economic shocks, innovations
JEL Classification: E0, C11, C3
Suggested Citation: Suggested Citation