Table 4.

Correlation matrix and variance inflation factor (VIF) statistics.

	$\mathit{ln}GDP$	$\mathit{ln}GCF$	$\mathit{ln}NRE$	$\mathit{ln}RE$	$\mathit{ln}GC$	$\mathit{ln}TO$
$\mathit{ln}GDP$	1
$\mathit{ln}GCF$	0.7700	1
$\mathit{ln}NRE$	0.8708	0.4270	1
$\mathit{ln}RE$	0.4529	0.5898	-0.7609	1
$\mathit{ln}GC$	0.8385	0.3992	0.2171	-0.2426	1
$\mathit{ln}TO$	0.7622	0.2448	0.3387	-0.1458	0.3416	1
Tolerance		1.961	2.781	1.717	1.125	1.876
VIF		0.510	0,360	0.582	0.889	0.533

The correlation matrix of the variables demonstrates the positive correlation among renewable and nonrenewable energy usage, government expenditure and trade openness. We also examine the level of multicollinearity among the variables, and the VIF coefficients show that multicollinearity is not a problem in our estimation.