"Economic theory developed in the prior literature indicates that under the joint and several liability imposed by the federal Superfund statute, the government should recover more of its costs of cleaning up contaminated sites than it would under nonjoint liability, and the amount recovered...

"Public policies for pollution control, including climate change policies, sometimes allow polluters in one sector subject to an emissions cap to offset excessive emissions in that sector with pollution abatement in another sector. The government may often find it more costly to verify offset...