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：双向固定效应（TWFE）模型在政治学因果面板分析中应用广泛。然而，近期方法论讨论指出，在存在异质性处理效应（HTE）及平行趋势假设（PTA）违反的情况下，该类模型的有效性面临挑战。这一新兴研究领域已提出多种估计量与诊断方法，但实证研究者因此在两个层面陷入困惑：基于TWFE模型现有结论的可靠性，以及当前最优实践方法。为应对这些问题，我们对三本顶尖政治学期刊中采用观察性面板数据与二元处理变量的37篇文章进行了检验、复制与再分析。通过运用六种新近提出的HTE稳健估计量，本研究发现：尽管估计精度可能受到影响，但TWFE模型推导的核心结论基本保持不变。然而，平行趋势假设违反与统计效能不足仍是可信推断面临的主要障碍。基于上述发现，我们提出了改进实证研究实践的建议。