Two decades have passed since the Clean Air Act Amendments of 1990 launched a grand experiment in market-based environmental policy: the SO₂ cap-and-trade system. That system performed well but created four striking ironies: First, by creating this system to reduce SO₂ emissions to curb acid...

Vintage-differentiated regulation (VDR) is a common feature of many environmental and other regulatory policies, wherein standards for regulated units are fixed in terms of the units' respective dates of entry, with later entrants facing more stringent regulation. In the most common application,...

Vintage-differentiated regulations (VDRs) are standards that are fixed with respect to the date of entry of regulated units, with later vintages facing more stringent standards. VDRs play prominent roles under major Federal, state, and local environmental laws. This paper synthesizes what is...

We describe three essential elements of an effective post-2012 international global climate policy architecture: a means to ensure that key industrialized and developing nations are involved in differentiated but meaningful ways; an emphasis on an extended time path of targets; and inclusion of...