Peer Effects on the United States Supreme Court

43 Pages Posted: 22 Feb 2019 Last revised: 10 Aug 2020

See all articles by Richard Holden

Richard Holden

University of New South Wales (UNSW)

Michael P. Keane

University of New South Wales

Matthew Lilley

Harvard University - Department of Economics

Date Written: August 10, 2020

Abstract

Using data on essentially every US Supreme Court decision since 1946, we estimate a model of peer effects on the Court. We consider both the impact of justice ideology and justice votes on the votes of their peers. To identify these peer effects we use two instruments that generate plausibly exogenous variation in the peer group itself, or in the votes of peers. The first instrument utilizes the fact that the composition of the Court varies from case to case due to recusals or absences for health reasons. The second utilizes the fact that many justices previously sat on Federal Circuit Courts. Those who served on the Circuit Courts for short (long) periods of time are empirically much more (less) likely to affirm decisions from their “home” court. We find large peer effects. Replacing a single justice with one who votes in a conservative direction 10 percentage points more frequently increases the probability that each other justice votes conservative by 1.6 percentage points. Further, a 10% increase in the probability that a given justice votes conservative leads to a 1.1 percentage point increase in the probability that each other justice votes conservative. This indirect effect increases the share of cases with a conservative outcome by 3.6 percentage points (excluding the direct effect of the new justice). In general, we find indirect effects are large relative to the direct mechanical effect of a justice’s own vote.

Suggested Citation

Holden, Richard and Keane, Michael P. and Lilley, Matthew, Peer Effects on the United States Supreme Court (August 10, 2020). UNSW Economics Working Paper 2019-01b, Available at SSRN: https://ssrn.com/abstract=3339242 or http://dx.doi.org/10.2139/ssrn.3339242

Richard Holden (Contact Author)

University of New South Wales (UNSW) ( email )

Kensington
High St
Sydney, NSW 2052
Australia

Michael P. Keane

University of New South Wales ( email )

Sydney, NSW
Australia

Matthew Lilley

Harvard University - Department of Economics ( email )

Littauer Center
Cambridge, MA 02138
United States

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