توسعه اقتصادی و تولید گازهای گلخانه ای: یک روش پانل ناپارامتری

We examine the empirical relation between CO2 emissions per capita and GDP per capita during the period 1960–1996, using a panel of 100 countries. Relying on the nonparametric poolability test of Baltagi et al. [Baltagi, B.H., Hidalgo, J., Li, Q., 1996. A nonparametric test for poolability using panel data, Journal of Econometrics 75, 345–367], we find evidence of structural stability of the relationship. We then specify a nonparametric panel data model with country-specific effects. Estimation results show that this relationship is upward sloping. Nonparametric specification tests do not reject monotonicity but do reject the polynomial functional form which leads to the environmental Kuznets curve in several studies.

The relationship between economic development and environmental quality has been extensively explored in recent years. The shape of this relationship has implications for the definition of an appropriate joint economic and environmental policy: depending on whether there is a negative or a positive influence of economic development on environmental quality, policy recommendations will differ. In the literature, this animated debate revolves around the existence of an Environmental Kuznets Curve (or inverted-U shaped curve, EKC), which implies that, starting from low levels of income per capita, environmental degradation increases, but after a certain level of income (turning point) it diminishes. Despite some exceptions, empirical studies are generally based on ad hoc parametric specifications with little attention paid to model robustness; yet different parametric specifications can lead to significantly different conclusions, and a functional misspecification problem is likely to occur. Popular parametric functional forms are linear, quadratic, and cubic polynomials in GDP per capita.

This paper investigates the empirical relationship between CO2 emissions and economic development using an international panel data set. We find evidence supporting specifications which assume the stability of the relationship between CO2 emissions per capita and GDP per capita over time during the period of the study. We show that within estimation of a parametric specification yields an EKC, but that the underlying strict exogeneity assumption of per capita GDP is rejected, whereas both the nonparametric and the first-difference estimations clearly contradict the existence of an EKC for CO2 emissions. Still, it also turns out that the parametric model is rejected against the nonparametric specification. How can we explain the monotonous relation between CO2 emissions per capita and economic development obtained in this study? Several arguments can be put forward. The earlier stages of economic development are associated with comparatively slow economic activities. One may think that at such a stage, obsolete technologies are still used. At the same time, government policies are more aimed at economic development than at environmental protection. Consequently, CO2 emissions rise with economic activities. In rich countries, the positive effect on emissions due to intensive economic activities seems to exceed the reduction in emissions due to the use of modern technologies. On the whole, the economic development process always results in increased CO2 emissions.