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arXiv 2312.05985econ.EMmath.STstat.MEstat.MLstat.TH
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交错采用下双重差分的融合扩展双向固定效应

Fused Extended Two-Way Fixed Effects for Difference-in-Differences With Staggered Adoptions

Gregory Faletto

AI总结:

提出机器学习估计量 FETWFE,通过单一调节参数自动选择参数限制,解决交错采用下双重差分的偏差与效率问题,并证明其一致性与渐近正态性。

摘要:

为了解决标准双向固定效应估计量在交错采用下双重差分中的偏差,Wooldridge (2021) 提出了扩展双向固定效应估计量,该方法增加了许多参数。然而,这降低了效率。将其中一些参数限制为相等(例如,同一队列内的后续处理效应)会有所帮助,但临时性限制可能会重新引入偏差。我们提出了一种具有单一调节参数的机器学习估计量,即融合扩展双向固定效应(FETWFE),它能够自动进行数据驱动的限制选择。我们证明,在适当的稀疏性假设下,FETWFE 以趋于 1 的概率识别出正确的限制,从而提高了效率。我们还证明了在条件或边际平行趋势下,FETWFE 对几类异质边际处理效应估计量具有一致性、oracle 性质和渐近正态性,并证明了在条件平行趋势下条件平均处理效应具有相同结果。我们提供了一个实现融合扩展双向固定效应的 R 包,并在模拟研究和实证应用中展示了 FETWFE。

英文摘要:

To address the bias of the canonical two-way fixed effects estimator for difference-in-differences under staggered adoptions, Wooldridge (2021) proposed the extended two-way fixed effects estimator, which adds many parameters. However, this reduces efficiency. Restricting some of these parameters to be equal (for example, subsequent treatment effects within a cohort) helps, but ad hoc restrictions may reintroduce bias. We propose a machine learning estimator with a single tuning parameter, fused extended two-way fixed effects (FETWFE), that enables automatic data-driven selection of these restrictions. We prove that under an appropriate sparsity assumption FETWFE identifies the correct restrictions with probability tending to one, which improves efficiency. We also prove the consistency, oracle property, and asymptotic normality of FETWFE for several classes of heterogeneous marginal treatment effect estimators under either conditional or marginal parallel trends, and we prove the same results for conditional average treatment effects under conditional parallel trends. We provide an R package implementing fused extended two-way fixed effects, and we demonstrate FETWFE in simulation studies and an empirical application.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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