The causal interpretation of panel vector autoregressions

Abstract

This paper discusses the different contemporaneous causal interpretations of Panel Vector Autoregressions (PVAR). I show that the interpretation of PVARs depends on the distribution of the causing variable, and can range from average treatment effects, to average causal responses, to a combination of the two. If the researcher is willing to postulate a no residual autocorrelation assumption, and some units can be thought of as controls, PVAR can identify average treatment effects on the treated. This method complements the toolkits already present in the literature, such as staggered-DiD, or LP-DiD, as it formulates assumptions in the residuals, and not in the outcome variables. Such a method features a notable advantage: it allows units to be ``sparsely'' treated, capturing the impact of interventions on the innovation component of the outcome variables. I provide an example related to the evaluation of the effects of natural disasters economic activity at the weekly frequency in the US.I conclude by discussing solutions to potential violations of the SUTVA assumption arising from interference.