Renewable energy, energy efficiency, and eco-friendly environment (R-E5) in Nigeria

Table 1 Augmented Dickey-Fuller, Philip-Perron, and KPSS unit root tests

Variables	ADF statistic	PP statistic	KPSS statistic
InREN_t	−7.1190*	−10.2891*	0.1288
ΔInREN_t	−4.5976*	−17.7251*	0.18848**
InPOP_t	−3.5147	−1.7788	0.057359
ΔInPOP_t	−3.7071**	−3.8137*	0.1880**
InGDP_t	−5.2226*	−5.2407*	0.0770
ΔInGDP_t	−8.1553*	−24.3946*	0.3493*
InFUEt	−2.9590	−2.9986	0.0578
ΔInFUE_t	−5.9338*	−6.8035*	0.2283*
InCO_2t	−1.8842	−1.8247	0.1413
ΔInCO_2t	−5.4920*	−6.0445*	0.1820**

The optimal lag order for ADF test is determined by AIC, while the bandwidths for PP and KPSS tests are determined by using the Newey-West Bartlett kernel (the unit root test indicates that all the variables are integrated or stationary at the first difference, I(1) except InREN_t and GDP_t which are stationary at levels)
*Significance at 1 % level; **significance at 5 % level; ***significance at 10 % level

ISSN: 2192-0567