When he was nominated to the Supreme Court, Chief Justice Roberts mentioned that one of his main objectives as chief justice would be to create more consensus on the Court and to forge a greater number of unanimous decisions. Lets see how successful he’s been after five years.
I considered October Terms 1995 – 2009. That includes ten terms under Chief Justice Rehnquist (OT95-OT04) and five terms under Chief Justice Roberts (OT05-OT09). I’ve excluded OT10 because the court tends to release unanimous opinions frequently in the beginning of the term and more divided opinions towards the end.
It doesn’t look like there has been much of a change, but there has been quite a bit of volatility during the Roberts Court. During OT05, for example, the Court split 5-4 in only 12% of cases but in the next term, OT06, the justices split 5-4 in a staggering 33% of cases.
Since OT05, the Court has split 5-4 in 12%, 33%, 17%, 29%, and 18% of cases, respectively. During the current term, there have been no 5-4 decisions and 68% (19 cases) have been unanimous. As I mentioned earlier, however, there will be significant deviation to the mean as the Court releases the most difficult decisions of the term.
*All of this data comes from SCOTUSblog stat packs.