Judges Judging Judges: Polarization in the U.S. Courts of Appeals

While prior literature has documented politicization in appellate decision-making, our focus — beyond replicating and extending this pattern — is on polarization, defined as differential treatment of trial judges who share the appellate panel members’ political affiliations. Using a dataset of more than 400,000 cases from 1985 to 2020, we document both phenomena. Panels with more Democratic-appointed judges are systematically more likely to reverse throughout the sample period. Polarization, however, emerges significantly only post-2000 and, while most pronounced in published cases, is present in both published and unpublished cases once reversal and publication are modeled jointly using a bivariate probit. Against a baseline reversal rate of 39 percent, moving from an all-Republican to an all-Democratic panel post-2000 increases the conditional reversal rate of Republican-nominated trial judges by approximately 9 percentage points — a 23 percent relative increase — and this effect is attenuated by roughly one-third when the trial judge is also Democratic-nominated. Polarization is strongest in ideological cases and persists among judges appointed pre-2000, indicating behavioral shifts beyond appointment effects. We find no evidence of gender-based polarization.