Table A1.

The results of panel unit root tests.

Variables	Level		First-Difference
	With Constant	Constant and Trend	Constant	Constant and Trend
LLC test
LNRAIN	0.0000	0.0000	0.0000 ***	0.0000 ***
LNSUNLIGHT	0.0000	0.0000
LNPERAGCARBON	0.0000	0.6145
LNMACHINE	0.0000	0.9993
Im, Pesaran, and Shin test
LNRAIN	0.0000	0.0000	0.0000 ***	0.0000 ***
LNSUNLIGHT	0.0000	0.0000
LNPERAGCARBON	0.9412	0.9974
LNMACHINE	0.4220	1.0000
ADF–Fisher chi-squared test
LNRAIN	0.0000	0.0000	0.0000 ***	0.0000 ***
LNSUNLIGHT	0.0000	0.0000
LNPERAGCARBON	0.9780	0.9100
LNMACHINE	0.5655	1.0000
PP–Fisher chi-squared test
LNRAIN	0.0000	0.0000	0.0000 ***	0.0000 ***
LNSUNLIGHT	0.0000	0.0000
LNPERAGCARBON	0.9921	0.9469
LNMACHINE	0.3202	1.0000
Breitung t-stat test
LNRAIN		0.0000		0.0000 ***
LNSUNLIGHT		0.0000
LNPERAGCARBON		0.8883
LNMACHINE		1.0000

Note: *** indicates that this column has 1% visibility.