Table 9.

The results of Robustness test.

Variables	h_DIGr		h_AIr		h_TYCr
	Coefficient	Standard error	Coefficient	Standard error	Coefficient	Standard error
L1.h_DIGr	0.682**	0.159	0.021***	0.023	6.892***	2.041
L1.h_AIr	0.816	1.946	0.662**	0.316	−77.152	117.629
L1.h_TYCr	−0.005	0.002	0.005	0.003	2.605***	3.383
L2.h_DIGr	−0.022**	0.012	0.002*	0.003	−2.412	1.690
L2.h_AIr	0.055	0.398	−0.305	0.192	65.005	146.937
L2.h_TYCr	−0.001	0.002	0.001	0.001	−3.146**	2.556
L3.h_DIGr	−0.001	0.011	−0.036	0.020	8.336	11.172
L3.h_AIr	−0.103	0.278	−0.180	0.279	90.645	83.063
L3.h_TYCr	0.009	0.015	0.002	0.001	2.552*	1.992

Note:*, * *, * * indicate significance at the confidence level of 10%, 5%, and 1%, respectively; h _ represents the form of eliminating fixed effect after Helmert transformation; L1, L2, and L3 indicate lag of one, two and three orders, respectively.