Doctor of Philosophy (PhD)


Agricultural Economics

Document Type



The relationship between pollution and per capita income generally appears as an inverted U-shaped curve. This inverted U-shaped curve is known as the environmental Kuznets curve (EKC). The shape of the curve, however, is very sensitive to the data, location and pollutant considered in the analysis. Since the early 1990s, there has been an exponential growth in the number of empirical studies in this field, but many refute the inverted U-shaped nature of the curve for pollutants across different time periods and geographical regions. This has generated an increased interest in developing a more flexible functional form for model specification and estimation. Our observation is that existing EKC studies have not fully utilized the advances in semiparametric and nonparametric panel econometrics. In order to identify an appropriate functional form between environmental quality and economic growth, we surveyed recent developments in econometrics specifically related to nonparametric and semiparametric models for panel data. We proposed a seemingly unrelated partial linear model (SUPLR) to address potential correlation between pollutants. Simulation study shows that the SUPLR model performs well for our data set. We examined the EKC relationship between water quality indicators (nitrogen, phosphorous, dissolved oxygen and mercury) and income at the watershed level, using environmental quality data from 53 parishes in Louisiana. Additionally, we explored the income-pollution relationship using Global Environment Monitoring System (GEMS) data from sixty eight countries. We found that the relationship followed an inverted U-shaped curve for nitrogen and dissolved oxygen and a cubic shape for mercury. At the global level, an inverted U-shaped relationship is found for three pollutants (dissolved oxygen, fecal coliform and coliform), a cubic relationship is found for three pollutants (mercury, chemical oxygen demand and biological oxygen demand) and an L-shaped relationship is observed for two pollutants (arsenic and lead). Model specification tests suggest that a semiparametric model is better specified to study the income-pollution relationship.



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Committee Chair

Paudel, Krishna P.