An Empirical Study of the Length of U.S. Supreme Court Opinions

Ryan C. Black and James F. Spriggs, II

Published 2008, Houston Law Review 45(3): 621-683 (Fall).


Scholars have become intensely interested in modeling law at the U.S. Supreme Court using a variety of indicators drawn from Court opinions. These include, for instance, examinations of the Court’s interpretation of precedent, use of jurisprudential reasoning, and citations to case law. Noticeably missing from such analyses is any focus on the length of majority opinions for the Court. Existing discussions of opinion length tend to consist of scholars, judges, or journalists bemoaning the general increase in the prolixity of the justices. We contend that opinion length is an interesting indicator of the Court’s work that deserves serious empirical inquiry. While some might think that the length of majority opinions results from the idiosyncrasies of individual authors or other somewhat random factors, we suggest that it will manifest empirical regularities capable of being systematically explained. We thus put forward a series of hypotheses and test them on data, first, regarding the length of the average majority opinion (measured based on the number of words in a majority opinion) from 1791 through 2005, and, second, on the length of individual opinions released between the 1969 and 1985 terms. Our results indicate that we can indeed empirically model the determinants of opinion length.

Download the article here.

Data and research findings described in Adam Liptak. 2010. "Justices are Long on Words but Short on Guidance." New York Times. November 17, 2010 (page A1).

Our opinion length data, merged with the Supreme Court Database, is available here. These are the data used in the Liptak article. The file is saved in Stata format. Please contact me if you'd like it in another format.