Adam Liptak of the New York Times has a column today about the influence of state supreme courts on each other: “Around the U.S., High Courts Follow California’s Lead.”

The column reports on a study that determined how many times the Shepard editors had used the “followed” designation to characterize one state supreme court’s citation of another. This sort of “citation analysis” is common among academics as a measure of prestige. Attempts to use it as a means to evaluate or rank courts have been met with more limited success. This study attempted to overcome some of those criticisms by focusing on the subset of citations that Shepards has classified as showing one court “following” another. ((Liptak explains:

The study counted only citations designated “followed” by Shepard’s. The designation is used relatively rarely and only for “controlling or persuasive authority,” meaning that the cited decision played a substantial role in shaping the later decision. A manual Shepard’s provides to the lawyers who work for it says that the “followed” designation should be used only if the citing decision “contains language beyond a ‘mere going-along’ with the cited case.” ))

The results: California was the most “followed,” by a mile. Liptak’s article notes that “New York comes in 10th and is only about half as influential as California, with 627 followed cases.” Barry Barnett at Blawgletter notes that Texas was 14th and that its “standing” falls to 20th in the time period 1986 to 2005. Blawgletter asks “We feel certain Their Honors have an excellent explanation.”

I don’t know, but I can offer one suggestion. ((I originally wondered whether the study took into account Texas’s bifurcated system in which criminal cases go to a different court, but that question is answered in footnote 18 of the study. The study data does in fact combine the decisions of the two courts. ))

By focusing on “follows,” the study gives greater weight to decisions that ground themselves in broad notions of the common law rather than some other source of authority, say, a statute passed by a legislature. My guess is that this means the study overweights decisions that expand common-law doctrines — such as tort law, privacy rights, and the like. By contrast, court decisions that contract such doctrines (such as tort reform) often cite as authority the state’s own idiosyncratic statutes rather than “following” another state’s lead.

With that in mind, it seems little wonder that the Supreme Court of California is the leader in “follows,” as it remains in the vanguard of creating new common-law doctrines. And for those who have followed the ebbs and flows of Texas politics, it also seems unsurprising that the Texas court is less likely to lead in that category in the 1990s and 2000s than it was in the 1960s and 1970s. (( Some of that change may reflect the judicial philosophy of the courts; much of it reflects the actions of the Texas Legislature. The California Supreme Court is, after all, presented with a very different set of statutes than is the Texas Supreme Court. ))

To me, this suggests a weakness in the study’s exclusive focus on the Shepards “followed” designation. While that measures something, it does not appear to be a useful measurement of overall influence.

(Via Blawgletter.)