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	Panelbaserad kvantitativ observationsforskning	Differens-i-differens (DiD)
Ämnesområde	Forskningsdesign	Ekonometri
Familj	Process / pipeline	Regression model
Ursprungsår	1960s–1980s (formalized in econometrics); widely adopted in social sciences by 1990s	1994
Upphovsperson	Established through econometrics literature; foundational contributions by Cheng Hsiao, Zvi Griliches, and Marc Nerlove	Card & Krueger (canonical 1994 application); Angrist & Pischke (textbook treatment)
Typ	Quantitative observational longitudinal design	Causal inference / panel regression
Ursprungskälla	Hsiao, C. (2003). Analysis of Panel Data (2nd ed.). Cambridge University Press. ISBN: 978-0521522717	Angrist, J. D., & Pischke, J.-S. (2009). Mostly Harmless Econometrics: An Empiricist's Companion. Princeton University Press. ISBN: 978-0691120355
Alias	panel observational study, longitudinal observational panel design, panel survey research, repeated-measures observational design	diff-in-diff, DiD, Farkların Farkı (Diff-in-Diff)
Närliggande	4	5
Sammanfattning	Panel-based observational quantitative research follows the same individuals, organizations, or units across two or more time points without experimentally manipulating any condition. By combining the within-unit depth of longitudinal tracking with the numerical precision of quantitative measurement, it enables researchers to study change over time, detect lagged effects, and control for stable unobserved characteristics — all while maintaining the ethical simplicity of pure observation.	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.