Before revision:  We also propose estimators of a dynamic linear model, with group-specific but time-invariant effects of the current and lagged treatments, which may be used to evaluate ex-ante the effect of future policies  .
After revision:  We also propose estimators of a dynamic linear model, with group-specific but time-invariant effects of the current and lagged treatments, which may be used to evaluate ex-ante the effect of future policies . In an application, we find that our estimators differ substantially from those obtained with dynamic two-way fixed effects regressions .