I suspect the issue is one of word processing and the Rehnquist Court's miserly approach to certiorari rather than one of clerks—though certainly the clerking issue redounds in other ways.

Maybe. Barone alleges a "step" increase in years when new clerks are added, which would make your theory less likely to explain that. Of course, since Rehnquist hires only 3 clerks and Stevens has until recently, there is a natural experiment possible. Do other justices' dissents and concurrences increase while Rehnquist's stay the same?

I will add that this natural experiment allows us to test other hypothetical benefits that come from fewer clerks. A classmate suggests that opinions might be shorter and have fewer footnotes, or that justice might be less able to rely on their clerks as a crutch. (We would just investigate to see if Rehnquist and Stevens had fewer footnotes or shorter comparative tenures on the bench than their more-staffed colleagues).

Presumably one would also one to track some variable along the lines of "Supreme Court clerks' free/social time," because of the emininently plausible scenario in which that variable swings widely to make up the posited gap in law-clerk working time. Admittedly it might be small to begin with (I don't know much about it, sadly), so one would want a high-precision measurement. One wouldn't want to suggest, for example, a proxy like "number of drinks consumed per Term-month," because it's highly unclear whether that would vary as an inverse or a direct function of the clerk-caseload.

Even though the number of cert petitions increase yearly, the Rehnquist Court accepts fewer cases proportionally and in actual numbers than prior Courts. With less cases to decide, there is more time to pontificate, especially with the assistance of many clerks. Meantime, some of the rejected petitions may have involved quite important issues that remained unaddressed by the Court.

After Massachusetts established an intermediate appeals court 30 years or so ago, I noticed that Supreme Judicial Court opinions got longer and longer. With less cases to decide, perhaps the SJC Justices decided to take advantage of the opportunity to pontificate.

Don't you just love the stream of citations that most of us do not have the time to read after wading through the opinion of the Court, concurring opinions and dissenting opinions, also with their streaming citations. How much of this is attributable to the clerks?

It is worth remembering that the S.C. is a court of law first, and an entertainment device for law students and political junkies second. "Citations" may make the thing duller reading for some (though I think they do not) but surely make it easier for actual attorneys and lower court judges to figure out What The Heck is Going On.

Breyer eschews footnotes, and would even if you gave him a dozen clerks.

I have to say I welcome dissents and concurrences and am glad that the justices have the manpower to be able to write them. Most Circuit court justices do not, and I believe that this artificially leads to the 80-90% unanimity most circuit panels enjoy. While that might make life easier for casereaders and casewriters, it might not make life easier for litigants or future litigants. These are important issues after all, at least for those who encounter them, and I think that the benefit outweighs the annoyances of the few.

As an aside, the number of concurrences and dissents creates an almost civil law environment where litigants cite to treatises, not cases. Here, the concurrences and dissents are commentary like treatises, with some persuasive value. Although in the U.S. (most) treatises are not treated as binding precedent, these "extra" opinions could be considered much-needed secondary sources by super-experts in the field.

If you include cert petitions, the Supreme Court has a unanimity rate far greater than 90%—and they don't have the advantage of a three-judge panel, where unanimity is simply easier to reach.