השוואת שיטות

	אומדן ההפרש הראשון	הפרש-בהפרשים (דיד)
תחום	אקונומטריקה	אקונומטריקה
משפחה	Regression model	Regression model
שנת המקור	2010	1994
הוגה השיטה	Jeffrey Wooldridge (treatment)	Card & Krueger (canonical 1994 application); Angrist & Pischke (textbook treatment)
סוג	Panel data estimator	Causal inference / panel regression
מקור מכונן	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
כינויים	FD Estimator, First-Difference Panel Estimator, First-Difference OLS, Birinci Fark Tahmincisi	diff-in-diff, DiD, Farkların Farkı (Diff-in-Diff)
קשורות	2	5
תקציר	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.