Limited Monotonicity and the Combined Compliers LATE
提出一种比现有单调性假设更弱的有限单调性假设，并识别出联合依从者的局部平均处理效应，该参数比两阶段最小二乘法识别的加权平均LATE更具政策相关性，且估计简单。
Abstract We consider endogenous binary treatment with multiple binary instruments. We propose a novel limited monotonicity (LiM) assumption that is generally weaker than alternative monotonicity assumptions in the literature. We define and identify (under LiM) the combined compliers local average treatment effect (CC-LATE), which is arguably a more policy-relevant parameter than the weighted average of LATEs identified by two-stage least squares (TSLS), and is identified under more general conditions. Estimating the CC-LATE is trivial, equivalent to running TSLS with one constructed instrument on a subsample. We use our CC-LATE to empirically assess how knowledge of HIV status influences protective behaviors.