Policy Evaluation with Nonlinear Trended Outcomes: Covid‐19 Vaccination Rates in the United States
非线性趋势结果的政策评价:美国新冠疫苗接种率
ABSTRACT This paper discusses pitfalls in two way fixed effects (TWFE) regressions when the outcome variables contain nonlinear and possibly stochastic trend components. If a policy change shifts trend paths of outcome variables, TWFE estimation can distort results and invalidate inference, especially in a context of evolving policy decisions. A robust solution is proposed by allowing for dynamic club membership empirically using a relative convergence test procedure. The…