This past summer, the Supreme Court lineup changed when Souter retired. So now’s a good time to look back at some statistics for the First Roberts Court. It started when O’Conner retired and then Rehnquist died in 2005. That ended the second Rehnquist court, which lasted 10 years. It was one of the longest lasting lineups. From Fall 2005 to summer 2009, the First Roberts Court made over 300 decisions. But O’Conner sat in for Alito for several of these until Alito got up to speed. So I limited the decisions to April 17, 2006 through June 2009, which contains 275 decisions. Roughly 1/3 of those were unanimous, 1/4 were 5-4 splits, and the rest fell somewhere in between.
The 5-4 splits are where the drama is especially when you consider the ideological split in the court. This split is clear when you line up the justices next to the one with which they most often agree.
This is an agreeable court. Notice at the ends of the spectrum, Stevens and Thomas agree half the time. If you look closely you’ll see the ideological split falls between Kennedy and Breyer. Breyer is considered moderately liberal and Thomas is the most conservative. Yet Kennedy agrees with them equally. This puts Kennedy in a powerful position. Out of 63 5-4 split decisions, Kennedy was the deciding opinion on all but 10. The best anyone else did was 22 dissenting opinions.
This chart shows all the decisions during the First Roberts Court.Green – majority opinionsYellow – dissenting opinionsWhite - abstainedS – Stevens, Souter or ScaliaG – GinsburgB – BreyerK – KennedyR – RobertsA – AlitoT – Thomas
Thomas is holding tight to the conservative end. He disagrees with the liberal end more than any other. Plus, out of 19 lone dissenting opinions, 8 are from Thomas. In the Second Request Court, O’Connor was the swing vote. [See this and this.] Out of all 275 decisions, Kennedy had a dissenting opinion only 22 times. That’s 8%. Twice as many 5-4 splits along ideological lines were conservative than liberal.
Even though the justices are likely to agree, it’s fun to see how much they disagree. This graph is similar to the agreement matrix above except it shows how much the justices disagree with each other.
You can see which justices are ideologically similar. You can see that Kennedy disagrees with the liberal end of the bench more than the conservatives.
Posted by Chuck Newman 
