The relationship between pollution and per capita income generally appears as an inverted U-shaped curve, which is known as the environmental Kuznets curve (EKC). A detailed survey of the literature on this topic indicates that practitioners continue to struggle to confirm a priori shape of the EKC. Existing studies have shown a semiparametric EKC model is better compared to a parametric EKC model. Hence, the EKC hypothesis can be tested more accurately using recent econometrics advances in nonparametric/semiparametric models. However, EKC literature is not keeping up with the latest advances in semiparametric/nonparametric models. We summarize the existing semiparametric/nonparametric studies conducted in EKC. We conclude by affirming the belief that a more flexible form of econometric modeling, rather than imposing an ad hoc functional form, should be used in econometric modeling of the EKC hypothesis.
JEL Classifications: C14,Q53