Published online by Cambridge University Press: 11 January 2021
This paper considers the estimation of dynamic causal effects using a proxy structural vector-autoregressive model with possibly nonstationary regressors. We provide general conditions under which the asymptotic normal approximation remains valid. In this case, the asymptotic variance depends on the persistence property of each series. We further provide a consistent asymptotic covariance matrix estimator that requires neither knowledge of the presistence properties of the variables nor pretests for nonstationarity. The proposed consistent covariance matrix estimator is robust and is easy to implement in practice. When all regressors are indeed stationary, the method becomes the same as the standard procedure.
We thank Donald Andrews, Peter Phillips, and two anonymous referees for their helpful comments. Xu Han would like to acknowledge the financial support by the GRF grant 11505515 from the Research Grants Council of Hong Kong S.A.R.