This Article presents findings from the most comprehensive empirical study to date on how the federal courts of appeals have applied Chevron deference— the doctrine under which courts defer to a federal agency’s reasonable interpretation of an ambiguous statute that it administers. Based on 1,558 agency interpretations the circuit courts reviewed from 2003 through 2013 (where they cited Chevron), we found that the circuit courts overall upheld 71% of interpretations and applied Chevron deference 77% of the time. But there was nearly a twenty-five-percentage-point difference in agency-win rates when the circuit courts applied Chevron deference than when they did not. Among many other findings, our study reveals important differences across circuits, agencies, agency formats, and subject matters as to judicial review of agency statutory interpretations.
Based on prior empirical studies of judicial deference at the Supreme Court, however, our findings suggest that there may be a Chevron Supreme and a Chevron Regular: whereas Chevron may not have much of an effect on agency outcomes at the Supreme Court, Chevron deference seems to matter in the circuit courts. That there is a Chevron Supreme and a Chevron Regular may suggest that, in Chevron, the Supreme Court has an effective tool to supervise lower courts’ review of agency statutory interpretations. To render Chevron more effective in creating uniformity throughout the circuit courts, the Supreme Court needs to send clearer signals on how courts should apply the deference standard.