In this paper we propose a solution to the non-robustness that plagues the estimation of inverted U-shaped relationships using panel data, such as the relation between pollution and income. When dependent and independent variable (like pollution and income) are both time related, separating the effect of the independent variable from time effects brings about a fundamental identification dilemma: the imposition of restrictions on the controls might drive the shape of the relationship between the dependent (pollution) and independent (income) variables. Our solution consists of imposing the very weak constraint that arbitrary cross-sectional units have the same relationship. We apply our methodology to two widely studied cases, namely, SO2 and CO2 emissions. Interestingly, our estimates are insensitive to the required subjective choices, but also strongly differ from the literature so far. We find consistent positive income effects for both cases and time effect estimates with a clear U-shaped trend for SO2-emissions but only slightly so for CO2-emissions.
Download Info
To download:
If you experience problems downloading a file, check if you have the
proper application to
view it first. Information about this may be contained
in the File-Format links below. In case of further problems read
the IDEAS help
page. Note that these files are not on the IDEAS
site. Please be patient as the files may be large.
As the access to this document is restricted, you may want to look for a different version under "Related research" (further below) or search for a different version of it.