Chinaʼs Economic Growth, Energy Efficiency, and Industrial Development: Nonlinear Effects on Carbon Dioxide Emissions

Table 4

ADF unit root test.

Variables	ADF test		PP test		Test result
	ADF statistics	value	PP statistics	value
lnCO2	−2.17972	0.4896	−2.028535	0.5715	Not smooth
ΔCO2	−4.45923	0.0008	−4.49406	0.0007	Smooth
lnPCG	−3.00289	0.1421	−2.73828	0.2266	Not smooth
ΔPCG	−3.03398	0.0393	−2.98796	0.0432	Smooth
lnEI	−2.2858	0.4332	−2.68155	0.2485	Not smooth
ΔEI	−3.00955	0.0411	−3.04345	0.0380	Smooth
lnIAV	−2.025325	0.2753	−2.882964	0.0546	Not smooth
ΔIAV	−4.672079	0.0024	−4.432691	0.0009	Smooth

Note. The symbols , , and mean significant at the level of 10%, 5%, and 1%, respectively.