The econometrics of the environmental Kuznets curve: an illustration using Australian CO2 emissions

Four econometric issues associated with the estimation and testing of the environmental Kuznets curve (EKC) are considered: (i) model specification with respect to the order of the polynomial, (ii) model specification with respect to the use of linear or log-linear specifications, (iii) integration and cointegration considerations, and (iv) missing variables and time trends. These issues are examined in reference to Australian data on four measures of CO2 emissions and three measures of per capita income. While evidence is provided for an inverted U-shaped EKC, the results cannot be generalized. It is concluded that without the use of sensitivity analysis, the results are typically fragile.