Brett Kavanaugh’s confirmation to the US Supreme Court last week raised fears of a hyper-partisan SCOTUS and loss of public trust in the institution, especially in light of Kavanaugh’s highly emotional and partisan testimony at the Senate hearing on the allegations of sexual assault against him. But a new study offers a glimmer of hope, concluding that there are more consensus than partisan differences in SCOTUS decisions in the long run.
It is the first quantitative model to capture detailed correlations in SCOTUS judges’ voting patterns over time. Cornell University graduate student Eddie Lee created a hypothetical “Super Court” to study the voting patterns of Supreme Court justices who served from 1946 to 2016. Neither Kavanaugh nor the other recently confirmed judge, Neil Gorsuch, is included in the analysis, which was recently published in the Statistical Physics Journal. It builds on Lee’s 2015 study examining the voting patterns of the second Rehnquist court (1994-2005), which found that judges were much more inclined to unanimity in their decisions, despite their ideological differences.
It may seem strange to create such a Super Court scenario, but Lee argues that it makes sense to do so, given how many different judges overlap due to their lifetime tenures. So even if Judge A never actually voted with Judge C, both probably served at the same time (and thus voted with) Judge B. This makes it possible to infer when Judges A and C may have voted together.
“We can imagine that the judges are ‘coupled’ in such a way that ferromagnetic couplings correspond to ideologically similar judges.”
For his data analysis, Lee adapted a statistical model for magnetic behavior. “Just as the components of a magnet tend to align (ferromagnetism) or anti-align (anti-ferromagnetism), we can imagine that the judges are ‘coupled’ in such a way that ferromagnetic couplings correspond to ideologically similar judges,” he said. Lee has found a way to make that metaphor quantitative by measuring the links in the voice register. And he found that the voice patterns fit nicely with the magnetism model.
There was some evidence in the data of partisan voting blocs amid shifting alliances along ideological lines, but Lee found this to be a small part of the overall pattern on his hypothetical Super Court. Rather, any given justice would be found in a surprisingly diverse range of voting blocs, even on what we consider to be the most partisan issues. Over time, the court usually comes to a consensus, with strong (and sometimes surprising) correlations between the judges.
For example, the SCOTUS judges of the late 1800s under Chief Justice Morrison Waite made 9-0 decisions about 90 percent of the time. Although the court has become much less unanimous since the 1940s, Lee nevertheless found that unanimous decisions still happen between 30 and 50 percent of the time. That pattern of consensus spans nearly 100 years, an institutional timeline that far exceeds the tenure of even the longest serving judges.
In other words, “The court’s collective behavior over time reveals a stable institution isolated from the seemingly rapid pace of political change,” Lee says. It is in stark contrast to the much more volatile voting patterns among members of Congress, who have much more turnover.
All of this goes against the prevailing narrative of the daily news cycle, as well as the opinions of some Supreme Court scholars. “When you look at the complexity of voting over time, there’s no point in thinking about left versus right,” Lee says. “In the grand scheme of things, we might think of this particular Supreme Court as divided between left and right, but it’s not clear what it means to call the institution biased for a long time.”
DOI: Statistical Physics Journal2018. 10.1007/s10955-018-2156-0 (About DOIs).