Over the last decade, market-based incentives have become the regulatory tool of choice when trying to solve difficult environmental problems. Evidence of their dominance can be seen in recent proposals for addressing global warming (through an emissions trading scheme in the Kyoto Protocol) and for amending the Clean Air Act (to add a new emissions trading systems for smog precursors and mercury--the Bush administration's "Clear Skies" program). They are widely viewed as more efficient than traditional command and control regulation. This collection of essays takes a critical look at this...