Researchers using instrumental variables to investigate ordered treatments often recode treatment into an indicator for any exposure. We investigate this estimand under the assumption that the instruments shift compliers from no treatment to some but not from some treatment to more. We show that when there are extensive margin compliers only (EMCO) this estimand captures a weighted average of treatment effects that can be partially unbundled into each complier group's potential outcome means. We also establish an equivalence between EMCO and a two-factor selection model and apply our results to study treatment heterogeneity in the Oregon Health Insurance Experiment.

翻译：使用工具变量研究有序处理变量的研究者通常将处理变量重新编码为是否接受任何处理的指示变量。我们基于工具变量仅促使无处理组转向有处理组而不促使有处理组增加处理量的假设，研究这一估计量。我们证明，当仅存在广延边际依从者时，该估计量捕捉到的处理效应加权平均值可部分分解为各依从者组的潜在结果均值。我们还建立了广延边际依从者与双因子选择模型之间的等价关系，并将我们的结果应用于俄勒冈健康保险实验中的处理异质性研究。