So sánh phương pháp

	Ước lượng Sai phân Bậc nhất	Phương pháp Sai phân kép (Difference-in-Differences - DiD)
Lĩnh vực	Kinh tế lượng	Kinh tế lượng
Họ	Regression model	Regression model
Năm ra đời	2010	1994
Người khởi xướng	Jeffrey Wooldridge (treatment)	Card & Krueger (canonical 1994 application); Angrist & Pischke (textbook treatment)
Loại	Panel data estimator	Causal inference / panel regression
Công trình gốc	Wooldridge, J. M. (2010). Econometric Analysis of Cross Section and Panel Data (2nd ed.). MIT Press. ISBN: 978-0-262-23258-8	Angrist, J. D., & Pischke, J.-S. (2009). Mostly Harmless Econometrics: An Empiricist's Companion. Princeton University Press. ISBN: 978-0691120355
Tên gọi khác	FD Estimator, First-Difference Panel Estimator, First-Difference OLS, Birinci Fark Tahmincisi	diff-in-diff, DiD, Farkların Farkı (Diff-in-Diff)
Liên quan	2	5
Tóm tắt	The First-Difference (FD) estimator is a panel data method that eliminates unobserved, time-invariant individual heterogeneity by subtracting each unit's observation in period t-1 from its observation in period t. By operating on changes rather than levels, FD removes any fixed individual effect that would otherwise confound causal inference. It is widely used in labor economics, program evaluation, and applied microeconomics whenever researchers suspect persistent unobserved differences across individuals, firms, or countries.	Difference-in-Differences is a causal-inference method that estimates the effect of an intervention by comparing how a treatment group and a control group change over time. Made famous by Card and Krueger's 1994 minimum-wage study and developed in Angrist and Pischke's Mostly Harmless Econometrics, it isolates the treatment effect as the difference between the two groups' before-after changes.