A Phylogenetic Tree of Supreme Court Decisions #SCOTUS

A Phylogenetic Tree of Supreme Court Decisions #SCOTUS

The United States Supreme Court is composed of nine justices: John Roberts (JGR), Antonin Scalia (AS), Anthony Kennedy (AMK), Clarence Thomas (CT), Ruth Bader Ginsburg (RBG), Stephen Breyer (SGB), Samuel Alito (SAA), Sonia Sotomayor (SMS), and Elena Kagan (EK).

The matrix at the top of the following figure shows the percentage of agreements between pairs of justices. The first thing one notices is that there is relatively very little disagreement among the justices. The most disagreements are recorded for Ruth Bader Ginsburg versus Clarence Thomas, Ruth Bader Ginsburg versus Samuel Alito, and Sonia Sotomayor versus Clarence Thomas. But even these agree in 75% of the cases.

If one transforms the complementary matrix of disagreements into a neighboring joining tree rotted at mid point, one gets the picture at the bottom of the figure. The highest distance is between Sonia Sotomayor and Samuel Alito, which should represent the extremes of the sane rational left wing versus the crazy religious right wing, respectively.

The tree can be divided into three clades. 
The most tightly knit clade are the crazies, with Samuel Alito and Clarence Thomas particularly close to one another. No other two judges agree to such an extent, which raises the possibility that one of them does not think for itself but merely copies what the other one says. Antonin Scalia is somewhat distinct within the gaga crowd. 
The other clade is the sane left wing. The core of the left wing is a clade consisting of the three women on the court. Stephen Breyer is also there, but as an outgroup.

The chief justice and Anthony Kennedy form a third clade with very long branches that unfortunately clusters mostly with the loony nuts.

Chart (wouldn't copy):
http://ppr.li/r?trail=contributor%3Dtwitter%3A249329330&url=http%3A%2F%2Fjudgestarling.tumblr.com%2Fpost%2F111697513556%2Fa-phylogenetic-tree-of-supreme-court-decisions&urlhash=6a3fcd00
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