Scotusblog has put together a package of statistics about US Supreme Court rulings for the term so far (referred to as OT14).
Opinion Output: Justice Clarence Thomas currently leads his colleagues, with twenty-five total opinions authored through this week. Fifteen of those are dissenting opinions, including eleven that are ”substantive” opinions (those arbitrarily defined as being greater than five pages in length)… As in recent years, Justices Anthony Kennedy and Elena Kagan have authored the fewest opinions, with nine and eight total opinions, respectively. Chief Justice Roberts also has nine opinions for the Term, including five majority opinions, one concurring opinion, and three dissenting opinions.
Frequency in the Majority: Remarkably, Justice Stephen Breyer has been in the majority in all but two cases on the merits in which he has participated this year.
5-4 Cases: There have been eight 5-4 decisions thus far, only three of which divided along common ideological lines. Justice Breyer was in the majority for seven of the eight 5-4 cases, and Justice Sonia Sotomayor has the next-highest frequency in the majority of 5-4 cases. She was in the majority for six out of eight 5-4 decisions, but has yet to author any majority opinions in 5-4 cases during OT14. Justices Thomas and Antonin Scalia have each been in the majority of a 5-4 decision only twice during the Term.
I found the chart of the frequency of each justice in the majority to be particularly interesting. It turns out that for both unanimous and divided opinions, three of the so-called liberal judges (Breyer, Sotomayor, and Ginsburg) top the list. Scalia and Thomas easily lead the list of dissenting opinions, with fellow conservative Alito being a distant the third.
What this data suggest is that the strong conservatives (Scalia, Thomas, and Alito) are not that successful in winning over a majority to their views and that chief justice Roberts and justice Kennedy are the determiners of many of the final decisions, especially Roberts since he has the most say in how opinion authorship is assigned.