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Özbek et al. Carbon Footprints 2025, 4, 30 https://dx.doi.org/10.20517/cf.2025.43 Page 15 of 21

Table 6. Model-1 FMOLS and CCR (robustness) results
FMOLS (dependent variable:EF)
Variables
Coeff. Std. error t-statistic P-value
GDP 2.11 *** 0.54 3.89 0.00
***
GDP2 -0.14 0.04 -3.91 0.00
NREN 1.08 *** 0.15 7.30 0.00
*
TO -0.05 0.03 -1.75 0.09
***
C -10.34 1.98 -5.21 0.00
***
T -0.02 0.00 -5.12 0.00
Variables CCR (robustness)
Coeff. Std. error t-statistic P-value
GDP 2.17 *** 0.64 3.40 0.00
***
GDP2 -0.14 0.04 -3.37 0.00
NREN 1.09 *** 0.15 7.26 0.00
TO -0.05 0.03 -1.54 0.13
***
C -10.61 2.32 -4.58 0.00
***
T -0.02 0.00 -5.41 0.00
C denotes the constant term, and T denotes the train term. Adjusted R-squared values are 0.98 and 0.98 for the FMOLS and CCR estimations,
respectively. 10%, 5% and 1% significance levels are highlighted with *, and ***, respectively.

Table 7. Model-2 FMOLS and CCR (robustness) results
FMOLS (dependent variable:REN)
Variables
Coeff. Std. ERROR t-statistic P-value
***
GDP -14.15 2.66 -5.31 0.00
***
GDP2 1.02 0.20 5.13 0.00
TO 0.46 *** 0.13 3.46 0.00
URB 3.42 2.05 1.67 0.11
C 36.01 *** 11.85 3.04 0.00
*
T -0.12 0.07 -1.72 0.09
Variables CCR (robustness)
Coeff. Std. error t-statistic P-value
***
GDP -14.67 3.04 -4.83 0.00
***
GDP2 1.05 0.23 4.66 0.00
TO 0.48 *** 0.14 3.29 0.00
URB 3.48 2.29 1.52 0.14
C 37.63 *** 13.35 2.82 0.00
*
T -0.13 0.074 -1.83 0.08
C denotes the constant term, and T denotes the train term. Adjusted R-squared values are 0.972937 and 0.972505 for the FMOLS and CCR
estimations, respectively. 10%, 5% and 1% significance levels are highlighted with *, and ***, respectively.

Table 7 shows the coefficient estimation results for testing the RKC hypothesis. According to the FMOLS
results, a 1% increase in GDP, GDP2, NREN, and TO causes a 14.15% decrease, a 1.02% increase, a 0.46%
decrease, and a 3.42% increase in REN, respectively. These effects occur at a 1% significance level in GDP,
GDP2, and TO. The URB estimate is statistically insignificant. In addition, it is concluded that the C and T
terms are also significant in the estimate. As a result, the FMOLS test results show the validity of the RKC
hypothesis. According to FMOLS, the Model-2 turning point is obtained as = 6.94. Since this value
obtained is the elasticity coefficient, the equivalent of this value in dollars is approximately $1,033. This