Inferring Individual Preferences from Group Decisions: Judicial Preference Variation and Aggregation on Collegial Courts

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Extensive research on judicial politics has documented disparities in adjudication and biases in judging. Yet, lacking statistical methods to infer individual preferences from group decisions, existing studies have focused on courts publishing individual judges' opinions, leaving a gap in understanding collegial courts that report only collective and unanimous (`per curiam') panel decisions. We introduce a statistical methodology to identify the most fitting decision-theoretic models for such collective decisions, infer judges' individual preferences, and quantify the inconsistency in the court's decisions. This methodology is applicable in various small group decision-making contexts where group assignments are repeated and exogenous. Applying it to the Swiss appellate court for asylum appeals, where decisions are made in three-judge panels, we find that in 45% of cases, the panel chair can overrule the median judge. Although judges' preferences vary strongly with partisanship, the partially collective decision making of the panel moderates this heterogeneity.