Difference-in-Differences Designs: A Practitioner’s Guide
为研究者梳理了双重差分法的多种设计类型和估计量，涵盖协变量、权重、多期处理和交错处理等常见扩展，帮助实证研究者正确应用该方法。
Difference-in-differences (DiD) is arguably the most popular quasi-experimental research design. Its canonical form, with two groups and two periods, is well understood. However, empirical practices can be ad hoc when researchers go beyond that simple case. This article provides an organizing framework for discussing different types of DiD designs and their associated DiD estimators. It discusses covariates, weights, handling multiple periods, and staggered treatments. The organizational framework, however, applies to other extensions of DiD methods as well.