I've just come up with some estimates of this, based on samples from the first five months in 2007, and searches in MEGA;MEGA on Lexis. The estimates are only estimates, for a variety of reasons, but I think they're good ballpark judgments.

So my riddles to you:

(1) How many times per month do U.S. courts — in Lexis-accessible opinions — cite student-written law review articles (denominated Note, Comment, Case Note, and Casenote, though excluding faculty-written works denominated Comment)?

(2) How many times per month do U.S. courts cite non-student-written law review articles?

Let's see who can get closest to right, or at least closest to my estimates of what's right. (By the way, there are a total of about 25,000 Lexis-accessible cases put out per month.) [UPDATE: I should also note that there seem to be about 2500 student articles published per year, and about 9000 non-student articles.]

Last week I asked how often courts cite student articles, and how often they cite articles by nonstudents. So far, my research results are tentative -- I need to confirm them in a few ways, which I hope to do over the next several weeks. But my tentative answer is about 500 cites of student articles per year (the ones denominated Notes, Comments, and Casenotes, and not counting professor-written Comments), and 3000 cites of nonstudent articles. Every average weekday, two court decisions are citing a student article.

Moreover, it seems that there are about 3 times as many nonstudent articles published each year as there are student articles. It thus means that student articles are cited about 50% as often per article published as are nonstudent articles -- a higher ratio than I would have expected.

My estimate is also that there are about 15,000 cites of student articles per year.

Who came closest among the commenters? ElChato for the student articles, but he underestimate the academic articles by a factor of 3. Roger and guest314159265 came close for the professor articles, but they overestimated the student articles by a factor of pi. No, actually, by a factor of 10 for Roger and 5 for guest314159265. Dave N came closest to the right ratio, but underestimated both by a factor of roughly 8.

One commenter predicted: "You'll see lots more citation of student-written pieces in state-court appellate opinions than in federal-court appellate opinions." My tentative findings are contrary to this -- in my initial sample (and I'll go through the data in a somewhat broader sample in a few weeks), about half came from federal courts and about half from state courts. Of the recent decisions on Lexis, federal decisions made up about 40% and state decisions about 60% (though I'll have to recalculate this once I figure out how to omit the one-line orders), so the citation patterns seem roughly comparable.

Incidentally, less than a quarter of the state citations in my sample were to in-state articles focused on the law of the state involved; over 75% of the state citations were to articles dealing with nationwide (or out-of-state) issues.