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

Published online by Cambridge University Press:  18 November 2025

Dominik Hangartner
Affiliation:
Center of Comparative and International Studies, ETH Zurich, Zurich, Switzerland Immigration Policy Lab, ETH Zurich, Zurich, Switzerland
Benjamin E. Lauderdale
Affiliation:
Department of Political Science, University College London, London, UK
Judith Spirig*
Affiliation:
Immigration Policy Lab, ETH Zurich, Zurich, Switzerland Department of Political Science, University College London, London, UK Department of Political Science, University of Zurich, Zurich, Switzerland
*
Corresponding author: Judith Spirig; Email: j.spirig@ucl.ac.uk
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Abstract

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 courts’ 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 per cent of cases, the chair-as-dictator rule applies (rather than majority rule). Although judges’ preferences vary strongly with partisanship, the partially collective decision making of the panel moderates this heterogeneity.

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Article
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2025. Published by Cambridge University Press
Figure 0

Figure 1. Mapping between preferences and decisions.Note: the top two axes illustrate the mapping between preferences and hypothetical single-judge decisions. The bottom axis illustrates the three-judge decisions that are actually observed, indicating the range of cases over which decisions depend on which preference aggregation rule resolves the panel’s decision making.

Figure 1

Table 1. Overview of decision-theoretic rules

Figure 2

Table 2. Manipulation check and placebo tests

Figure 3

Table 3. Fit statistics for preference aggregation rules

Figure 4

Figure 2. Heterogeneity in judges’ preferences.Note: left panel: estimated preferences of judges (posterior means) from the best-fitting mixture model that controls for origin country and uses hierarchical priors on judges. Right panel: same model but with party- rather than judge-specific estimates. Comparisons between neighboring parties show the probability that the party above is more lenient than the party below. The sample consists of 1,739 three-judge panel decisions (granted/rejected) on cases submitted in 2007. Both panels show posterior means along with 90 per cent (bold lines) and 95 per cent (thin lines) credible intervals. Mixture probability for chair model: λ1 = 0.45. Black dashed line indicates the average judge preference of 13.4 per cent (country of origin effect set to ‘Sri Lanka’). Party acronyms: Christian Democrats (CVP; 351 cases); Free Democratic Party (FDP; 408 cases); non-partisan (Indep; 487 cases); Social Democrats (SP; 334 cases); Swiss People’s Party (SVP; 159 cases).

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