| The 1990 U.S. Clean Air Act Amendments (CAAA) instituted a national program in tradable sulfur dioxide (SO2) emission permits, referred to as "emission allowances," in the U.S. electricity sector. This paper provides a survey and assessment of the SO2 allowance trading program with a focus on the role of innovation. Over the last decade the cost of compliance has fallen dramatically compared with most expectations, and today the total cost of the program is 40-140% lower than projections (depending on the timing of those projections and the counter-factual baseline considered). Marginal costs of reductions are less than one-half the cost considered in most analyses at the time the program was introduced. Innovation accounts for a large portion of these... |
