The literature that tests for U-shaped relationships using panel data, such as those between pollution and income or inequality and growth, reports widely divergent (parametric and non-parametric) empirical findings. We explain why lack of identification lies at the root of these differences. To...

We study the impact of human capital and the level of education on the pollution-income relationship controlling for income inequality in 17 OECD countries. By applying an innovative approach to country grouping, based on the temporal evolution of income inequality and clustering techniques to...