手法を比較

	クロスオーバー自然実験	差分の差 (Difference-in-Differences, DiD)
分野	実験計画法	計量経済学
系統	Process / pipeline	Regression model
提唱年	Crossover designs: mid-20th century; applied to natural experiments: 1990s–2000s	1994
提唱者	Drawn from crossover trial methods (Jones & Kenward) and natural experiment tradition (Mill, 1843; Dunning, 2012)	Card & Krueger (canonical 1994 application); Angrist & Pischke (textbook treatment)
種類	Quasi-experimental design	Causal inference / panel regression
原典	Dunning, T. (2012). Natural Experiments in the Social Sciences: A Design-Based Approach. Cambridge University Press. ISBN: 978-1107698000	Angrist, J. D., & Pischke, J.-S. (2009). Mostly Harmless Econometrics: An Empiricist's Companion. Princeton University Press. ISBN: 978-0691120355
別名	within-unit natural experiment, reversal natural experiment, crossover quasi-experiment	diff-in-diff, DiD, Farkların Farkı (Diff-in-Diff)
関連	5	5
概要	A crossover natural experiment exploits an externally imposed condition — a policy change, law, or environmental event — that exposes the same units (individuals, regions, firms) to both treatment and control states at different times. By observing each unit in multiple conditions, researchers use within-unit variation to estimate causal effects without researcher-controlled randomization, combining the internal validity advantage of crossover designs with the real-world relevance of natural experiments.	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.