We present a new estimator for causal effects with panel data that builds on insights behind the widely used difference-in-differences and synthetic control methods. Relative to these methods we find, both theoretically and empirically, that this “synthetic difference-in-differences” estimator has desirable robustness properties, and that it performs well in settings where the conventional estimators are commonly used in practice. We study the asymptotic behavior of the estimator when the systematic part of the outcome model includes latent unit factors interacted with latent time factors, and we present conditions for consistency and asymptotic normality. (JEL C23, H25, H71, I18, L66)

中文翻译：

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综合差值

我们使用面板数据提出了一种新的因果效应估计量，该估计量建立在广泛使用的差异差异和综合控制方法背后的见解之上。相对于这些方法，我们在理论上和经验上都发现，这种“综合差中差”估计器具有理想的鲁棒性，并且在传统估计器在实践中普遍使用的环境中表现良好。当结果模型的系统部分包括与潜在时间因素相互作用的潜在单位因素时，我们研究估计量的渐近行为，并且我们提出了一致性和渐近正态性的条件。(JEL C23, H25, H71, I18, L66)