When in Rome. . . Do Less Knowledgeable Judges Mimic their Peers?

Abstract

This paper examines the effect of ambiguity on judicial decisions and how judges anchor their decisions on their peers’ judgments. We also show that this effect is mitigated the more knowledgeable the judge is in a particular subject, which is consistent with the comparative ignorance hypothesis. We profit from the migration of judges between different judiciary districts to estimate how their writing and substantive judicial decisions change when they have different colleagues. The study focuses on health litigation cases from 2011 to 2022, in the first instance of S˜ao Paulo State Court, Brazil, which allows for a clean control of different subjects. The findings indicate that judges change their pattern of decision when they migrate to a new district court, becoming more similar to their new peers and more dissimilar to their former peers. The effect of anchoring decisions on peers is mitigated as judges become more experienced in a particular subject. The results of the study have important implications for the design of judicial institutions to preserve independent judgments and the benefits of aggregating different perspectives on a subject, also known as the “wisdom of crowds.