Two-way fixed effects (TWFE) models are ubiquitous in causal panel analysis in political science. However, recent methodological discussions challenge their validity in the presence of heterogeneous treatment effects (HTE) and violations of the parallel trends assumption (PTA). This burgeoning literature has introduced multiple estimators and diagnostics, leading to confusion among empirical researchers on two fronts: the reliability of existing results based on TWFE models and the current best practices. To address these concerns, we examined, replicated, and reanalyzed 37 articles from three leading political science journals that employed observational panel data with binary treatments. Using six newly introduced HTE-robust estimators, we find that although precision may be affected, the core conclusions derived from TWFE estimates largely remain unchanged. PTA violations and insufficient statistical power, however, continue to be significant obstacles to credible inferences. Based on these findings, we offer recommendations for improving practice in empirical research.

翻译：在政治科学因果面板分析中，双向固定效应（TWFE）模型应用广泛。然而，近期方法论讨论指出，当存在异质性处理效应（HTE）以及平行趋势假设（PTA）被违反时，这类模型的有效性受到质疑。新兴文献提出了多种估计量与诊断方法，导致实证研究者面临两大困惑：基于TWFE模型既有结论的可靠性，以及当前最佳实践方案。为回应这些问题，我们检验、复制并重新分析了来自三本顶级政治科学期刊中采用观测面板数据且涉及二元处理的37篇论文。通过使用六种新提出的HTE稳健估计量，我们发现虽然估计精度可能受影响，但源自TWFE估计的核心结论基本保持稳定。不过，平行趋势假设违反与统计效力不足仍是实现可靠推断的重大障碍。基于上述发现，我们为改进实证研究实践提出了具体建议。