Short-Run Implications of Cap-and-Trade versus Baseline-and-Credit Emission Trading Plans: Experimental Evidence

Two approaches to emissions trading are cap-and-trade, in which an aggregate cap on emissions is distributed in the form of allowance permits, and baseline-and-credit, in which firms earn emission reduction credits for emissions below their baselines. Theoretical considerations suggest the long-run equilibria of the two plans will differ if baselines are proportional to output, because a variable baseline is equivalent to an output subsidy. This is in opposition to the prediction that when output capacity is fixed, the short-run equilibria of the two plans will be identical. As a first step towards testing the long-run model, this paper reports on a laboratory experiment designed to test the shortrun prediction. A computerized environment has been created in which subjects representing firms choose emission technologies under fixed output capacity and participate in markets for emission rights and for output. Demand for output is simulated. All decisions are tracked through a double-entry bookkeeping system. Our evidence supports the theoretical prediction that the two trading mechanisms yield similar outcomes, however both exhibit significant deviation from the predicted equilibrium.