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MICHIGAN v. EPA KAGAN, J., dissenting
the emissions levels already achieved by the bestperforming members of the same group—benchmarks necessarily reflecting those plants’ own cost analyses. EPA then adopted a host of measures designed to make compliance with its proposed emissions limits less costly for plants that needed to catch up with their cleaner peers. And with only one narrow exception, EPA decided not to impose any more stringent standards (beyond what some plants had already achieved on their own) because it found that doing so would not be cost-effective. After all that, EPA conducted a formal cost-benefit study which found that the quantifiable benefits of its regulation would exceed the costs up to nine times over—by as much as $80 billion each year. Those benefits include as many as 11,000 fewer premature deaths annually, along with a far greater number of avoided illnesses. Despite that exhaustive consideration of costs, the Court strikes down EPA’s rule on the ground that the Agency “unreasonably . . . deemed cost irrelevant.” Ante, at 15. On the majority’s theory, the rule is invalid because EPA did not explicitly analyze costs at the very first stage of the regulatory process, when making its “appropriate and necessary” finding. And that is so even though EPA later took costs into account again and again and . . . so on. The majority thinks entirely immaterial, and so entirely ignores, all the subsequent times and ways EPA considered costs in deciding what any regulation would look like. That is a peculiarly blinkered way for a court to assess the lawfulness of an agency’s rulemaking. I agree with the majority—let there be no doubt about this—that EPA’s power plant regulation would be unreasonable if “[t]he Agency gave cost no thought at all.” Ante, at 5 (emphasis in original). But that is just not what happened here. Over more than a decade, EPA took costs into account at multiple stages and through multiple means as it set emissions limits for power plants. And when making its