Beyond plausibly exogenous
结合两种最新方法，先估计工具变量对结果的直接影响，再用该估计值进行敏感性分析，以检验和放松排除限制条件，并通过两个实证案例展示其应用。
We synthesize two recent advances in the literature on instrumental variable (IV) estimation that test and relax the exclusion restriction. Our approach first estimates the direct effect of the IV on the outcome in a subsample for which the IV does not affect the treatment variable. Subsequently, this estimate for the direct effect is used as input for the plausibly exogenous method developed by Conley, Hansen and Rossi. This two‐step procedure provides a novel and informed sensitivity analysis for IV estimation. We illustrate the practical use by estimating the causal effect of (a) attending Catholic high school on schooling outcomes and (b) the number of children on female labour supply.