Abstract: Over the last half decade, a variety of federal legislative proposals for limiting greenhouse gas (GHG) emissions have been put forward, most of which would set a price on carbon. As of early 2013, the one politically plausible policy appears to be a carbon tax, passed as part of a larger fiscal reform package. Meanwhile, the US Environmental Protection Agency has begun regulating GHG emissions from a variety of sources using its authority under the Clean Air Act. It may be necessary to choose between these two policies, however. The Waxman–Markey cap-and-trade bill that failed in 2009 would have preempted much of this authority, and it appears likely that a carbon tax law would do the same. But how can one make this choice? What are the key questions and issues to consider? The purpose of this paper is to compare these policies. Our aim here is therefore not to determine whether an exchange is wise or unwise. Instead, our intention is to give policymakers and other interested readers an impartial assessment of both policies and, in particular, the features that are important to a comparative evaluation. We don’t give answers, but hope at least to give the right questions to ask.

Abstract: New Corporate Average Fuel Economy (CAFE) standards were recently passed in the United States with the twin goals of reducing greenhouse gas emissions and oil use. The new standards represent a dramatic change from recent policy. This paper examines the key features of the new rules, and compares them to previous CAFE standards in terms of flexibility and structure. The importance of consumer preferences and market forces on CAFE outcomes are identified. In the second part of the paper, the perspective of the consumer is explored. Consumer assessments of fuel economy savings with more fuel-efficient vehicles may be biased or incomplete, leading many to argue that there is an “energy efficiency gap” in consumer demand for vehicles. Reasons for such a gap, such as market failures, behavioral responses, and market barriers, are summarized. The implications for policy are discussed, including the role of combining CAFE with other policies.