As we mentioned in our inaugural post, the California Supreme Court is worthy of special attention—not to mention a practice blog devoted to it—because it is a particularly important court in so many respects. One concrete measure of the Court’s importance is how often its decisions are followed by the highest courts of other states.

In December 2007, Jake Dear, the Court’s Chief Supervising Attorney, and Edward W. Jessen, the Reporter of Decisions of California, documented just how often the California Supreme Court is followed by other states’ high courts in their article “Followed Rates” and Leading State Cases, 1940-2005, 41 U.C. Davis L. Rev. 683. As their analysis, undertaken with the assistance of Lexis-Nexis, reveals, “the California Supreme Court has long been, and continues to be, the most ‘followed’ state supreme court.” Specifically, their research revealed, among other things, that between 1940 and 2005, 1,260 of the California Supreme Court’s decisions have been followed at least once by another state’s supreme court. The Washington Supreme Court was next, with 942 followed decisions. The median for all fifty state high courts was 453.

But what is particularly interesting is how often the decisions of the California Supreme Court are followed multiple times by other states’ supreme courts. Between 1940 and 2005, 160 of the Court’s decisions were followed three or more times by other states’ high courts. Washington was again second, but with just 72 decisions cited three or more times. When focusing on the most recent two decades (1986 to 2005), the ratios changed somewhat, but California remained in the lead. In that period, other states’ high courts cited 61 of the Court’s decisions three or more times. Washington was again second with 50 such decisions and Massachusetts was in third place with 37 decisions followed three or more times.

What does all this mean, and why is the California Supreme Court consistently cited more than other states’ supreme courts? It’s unclear, say Dear and Jessen. They note that a jurisdiction’s population, “and the available pool of diverse and cutting edge litigation” is an important factor, but they say “the data suggest it is far from determinative.” Ultimately Dear and Jessen suggest it may be the quality of the jurisprudence that matters most: “We continue to believe that a very important factor in this regard is the ‘culture’ of the court and its resulting written decisions. Are the opinions short and summary with little probing analysis? If so, they are less likely to be influential, or to be followed. Are the decisions analytical and cogent, surveying the field? If so they are more likely to be perceived by other courts as both carefully considered and well reasoned —and hence more likely to be followed.”