This paper examines the interdependence between imperfect competition and emis- sions trading in a two-sector (clean and dirty) economy. We compare the welfare implica- tions of an absolute cap-and-trade scheme (permit trading) with a relative intensity-based scheme (credit trading). We nd unambiguously more clean rms in the long run under credit trading. However, neither emissions trading con guration creates the rst-best out- come: there are too few (many) clean rms under permit (credit) trading. Permit trading dominates credit trading in terms of overall welfare at the long run equilibrium, except when policy is relatively lenient. It is also demonstrated that stricter policy does not necessarily induce the clean sector to grow relative to the dirty sector and we determine under what conditions this holds
