Emissions Variability in Tradable Permit Markets with Imperfect Enforcement and Banking

Unexpected variation in emissions can have a substantial impact on the prices and efficiency of tradable emission permit markets. In this paper we report results from a laboratory experiment in which subjects participate in an emissions trading market in the presence of emissions uncertainty. Subjects face exogenous, random positive or negative shocks to their emission levels after they make production and emission control plans. In some sessions we allow subjects to bank their unused permits for future use. In all sessions, subjects can trade in a reconciliation period to buy or sell extra permits following the shock realization. Subjects then report their emissions to the regulatory authority and they are placed in different inspection groups depending on their compliance history. The design of our experiment allows us to identify important interactions between emission shocks, banking, compliance and enforcement. We find that the relationship between emission shocks and price changes is significantly stronger without banking, so banking helps smooth out the price variability arising from the imperfect control of emissions. This greater price stability comes at a cost, however, since noncompliance and emissions are significantly greater when banking is allowed.