On the examination of the decoupling effect of air pollutants from economic growth: a convergence analysis for the US

The scope of this study is twofold. First, three alternative decoupling indicators associated with the related global (carbon dioxide emissions) and local air pollutants (e.g., sulfur dioxide and nitrogen oxide emissions) for the US regions are estimated over the period 1990–2017 based on eight related decoupling criteria. Second, by employing the Phillips and Sul methodology, we examine for the first time in the literature whether the three decoupling indicators converge among the US regions. The adopted algorithm rejects the convergence hypothesis for the whole sample, leaving room for the existence of several formulated clubs among the US regions. The findings indicate that for the carbon dioxide decoupling indicator three (merged) US regions converge to a steady state, while for sulfur dioxide and nitrogen oxide, two and seven convergence (merged) clubs are present. The transition paths validate the convergence test results. Lastly, this study puts forward some useful policy implications.