$Δ D_{i t} = α + β D E F_{i t} + є_{i t}$
	sample 1 (1)	sample 2 (2)	sample 3 (3)
β	0.109376*** (0.0000)	0.145617*** (0.0000)	0.189042*** (0.0000)
N	1212	1212	1212
R²	0.087667	0.132549	0.321912
F-test	58.03887***	92.29329***	159.0365***