Higher than any other Justice. So Roberts did not cite a single law review, but cited teh most amici. I suppose this says something about how he views academics, and how he views attorneys who submit briefs. What would be interesting, though, is how many of the amici he cited were authored by academics.
The justice least likely to cite an amicus brief is… Justice Antonin Scalia. Last year, he cited amicus briefs in only 12% of his opinions. Justice Scalia’s sparing approach is consistent with his past statements noting the limitations of amicus briefs. See Roper v. Simmons, 543 U.S. 551, 617- 18 (2005) (Scalia, J., dissenting). More surprising, however, is that Justice Stephen Breyer — who has stated that amicus briefs help improve the quality of high court decisions (Collins, supra, at 4) — had the second-lowest citation rate. Justice Breyer cited amicus briefs in only three of his 20 opinions last year (15%). The top amicus citers, by contrast, were the newest members of the Court, as reflected in the accompanying chart. Last term, Justices Elena Kagan and Sonia Sotomayor both cited amicus briefs in more than 60% of their opinions. Only Chief Justice John Roberts Jr. cited amici at a higher rate; seven of his 10 opinions cited at least one amicus brief. Interestingly, even though a justice’s propensity to cite amicus briefs does not appear to correspond with ideology, Justice Anthony Kennedy landed in the middle once again