According to the Coase theorem, if property rights to pollute are clearly established and emissions permit markets nearly eliminate transaction costs, the permit market equilibrium will be independent of how the permits are initially distributed among …firms. Testing the independence of …firms' permit allocations and emissions is difficult because of endogeneity and omitted variable bias. We exploit the random assignment of …firms to different permit allocation cycles in Southern California's RECLAIM Program to test for a causal relationship between facility-level emissions and initial permit allocations. Our primary …finding is that a null hypothesis of zero effect cannot be rejected.