Ruminant Eructation and a Long-Run Environmental Kuznets' Curve for Enteric Methane in New Zealand: Conventional and Fuzzy Regression Analysis

This paper examines the very long-run relationship between income and emissions of enteric methane in New Zealand, over the period 1895 to 1996. Controlling the emissions of this particular greenhouse gas is of crucial importance if that country is to meet its obligations as a signatory to the Kyoto Protocol. We use standard parametric regression, nonparametric regression, and a new nonlinear regression estimator based on fuzzy clustering analysis, to estimate 'environmental Kuznets' curves' for methane in New Zealand. Our results appear to be the first to support the existence of some form of 'inverted-U' curve for this pollutant, and the 'double-hump' relationship that emerges from our fuzzy modeling is consistent with certain theoretical results. Methane pollution is maximized at a level of real per capita GDP that is consistent with those reported for other pollutants in the literature.