Do collective actions clear common air? The effect of international environmental protocols on sulphur emissions

This paper considers the effects of voluntary international environmental protocols on emissions, in particular the effect of the 1985 Helsinki Protocol and the 1994 Oslo Protocol on the reduction of sulphur oxides. The analysis employs panel data from 30 European countries over the period between 1960 and 2002. We divide all countries into 'signatories' and 'controls', i.e., those that have signed and ratified a specific protocol and those that have not. Using a difference-in-difference panel data regression model, including yearly dummies and country-specific quadratic growth trajectories, we find no significant effect of either the Helsinki or the Oslo agreement in reducing sulphur emissions.