Measuring the effectiveness of international environmental regimes

Although past research has emphasized the importance of international regim es for international governance, systematic assessments of regime effects a re missing. This article derives a standardized measurement concept for the effectiveness of international environmental regimes. It is based on a sim ultaneous evaluation of actual policy against a no-regime counterfactual an d a collective optimum. Subsequently, the empirical feasibility of the meas urement concept is demonstrated by way of two international treaties regula ting transboundary air pollution in Europe. The results demonstrate that th e regimes indeed show positive effects-but fall substantially short of the collective optima.