Abstract. The number of studies seeking to empirically characterize the reduced-form relationship between a country economic growth and the quantity of various pollutants produced has recently increased significantly. In several cases researchers have found evidence in favor of an inverted-U "environmental Kuznets" curve. In the case of a major greenhouse gas, CO 2 , however, the evidence is at best mixed. This paper attempts to shed further light on this issue by using a newly developed data set covering over one hundred countries around the world for the last twenty five years and by considering alternative functional forms together with an effort to rigorously discriminate among competing alternatives.
DESPERATELY SEEKING (ENVIRONMENTAL) KUZNETS
Non-Technical SummaryThe relation between economic development and environmental quality is a very complex issue. For this reason, in the last few years several studies have tried to characterize this problem as an empirical reduced-form relationship. In particular, a few studies have identified a bell shaped curve for the pollution intensity of GDP. This behavior implies that, starting from low (per capita) income levels, (per capita) emissions or concentrations tend to increase but at a slower pace. After a certain level of income, emissions or concentrations start to decline as income further increases. In the case of a major greenhouse gas, CO 2 , however, the evidence of an inverted-U "Kuznets curve" is at best mixed.While all the studies have focused upon the empirical emergence of the environmental Kuznets curve and have typically discussed its implications with special reference to the value of the income turning point, the analysis concerning the robustness of the basic findings has not been, somewhat surprisingly, a major concern. The issue of the functional form for the reduced-form relationship between CO 2 emissions and GDP appears to be critical for the emergence of a bell shaped curve and for the crucial policy implications that could be drawn from such an empirical finding.We argue in this paper that the empirical relationship between a country GDP and CO 2 emissions ought to undergo a more careful scrutiny from at least two standpoints. In this paper we start from the observations that nearly all papers in this literature use the same source of data for CO 2 emissions and almost invariably fit to the data either linear-in-variables or log-linear functional relationships. Departing from this practice, we estimate the "standard" relationship on a newly developed data set for emissions. We also apply the theory of non-nested hypothesis testing in the attempt to choose between linear and log-linear models. After having noted a few theoretical and empirical drawbacks of these functional specifications, we propose two alternative functional forms, Gamma and Weibull, which are subsequently implemented. The estimated results are satisfactory and the features of the EKC relationship reasonable. Finally, interestingly enough non-nested tests produce the unambi...