Tolerating defiance? Local average treatment effects without monotonicity

• 成果类型: Article
• 署名作者: De Chaisemartin, Clement
• 署名单位: University of California System; University of California Santa Barbara
• 刊物名称: QUANTITATIVE ECONOMICS
• ISSN/ISSBN: 1759-7331
• DOI: 10.3982/QE601
• 发表日期: 2017
• 页码: 367-396
• 关键词: Monotonicity; defiers; instrumental variable; average treatment effect; partial identification

摘要

Instrumental variables (IVs) are commonly used to estimate the effects of some treatments. A valid IV should be as good as randomly assigned, it should not have a direct effect on the outcome, and it should not induce any unit to forgo treatment. This last condition, the so-called monotonicity condition, is often implausible. This paper starts by showing that actually, IVs are still valid under a weaker condition than monotonicity. It then derives conditions that are sufficient for this weaker condition to hold and whose plausibility can easily be assessed in applications. It finally reviews several applications where this weaker condition is applicable while monotonicity is not. Overall, this paper extends the applicability of the IV estimation method.