This digital document is a journal article from Journal of Environmental Economics and Management, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.Description: We consider the effects of international environmental agreements using the 1988 Sofia Protocol on the reduction of nitrogen oxides. Panel data on 23 European countries for the period 1985-96 is used to evaluate the impact on emissions by dividing countries into participants and non-participants: that is, those that did and those that did not ratify the Sofia Protocol. Using a difference in difference estimator and controlling for country-specific variables, we find that signing the treaty had a significant positive impact on emission reduction. The estimated yearly reduction in emissions is approximately 2.1% greater than it would have been without the Sofia Protocol.