Overruled precedents last an average of twenty years.
LeRoy '14 [Michael H; Professor, School of Labor and Employment Relations, and College of Law, University of Illinois at Urbana-Champaign; "DEATH OF A PRECEDENT: SHOULD JUSTICES RETHINK THEIR CONSENSUS NORMS?";and Lecturer, University of Chicago Law School.; Hofstra Law Review, Vol. 43: Iss. 2, Article 3; pp. 394-395; https://scholarlycommons.law.hofstra.edu/cgi/viewcontent.cgi?article=2795&context=hlr; ror]
1. Descriptive Statistics Passage of Years to Overrule a Precedent: How long do overruled precedents last? My sample contained 205 pairs of overruled and overruling precedents. Table 1.1 shows the longevity of overruled precedents in years.' 44 The range in Table 1.1 was 1 to 138 years. Overruled precedents lasted a mean of 29.11 years and median of twenty years. Table 1.2 compares the longevity of overruled precedents in Sidney Ulmer's 1959 study and my analysis. The main finding is that more precedents had a shorter duration in Ulmer's study, with 64% of overruled cases occurring within twenty years compared to 51% in my study. Some caveats must be noted in this comparison. My sample contained overruled cases that were decided before Ulmer's study. The fact that I had the benefit of a powerful online research tool may explain why Ulmer missed some cases. Also, the differences in our data could be due to sampling bias by Ulmer, or both of us. One or both of us could improperly include or exclude overruled cases. It is important to note that Ulmer did his research in the late 1950s. This was only twenty years or so after the Supreme Court experienced a major upheaval in commerce clause cases. Thus, the longer-lasting precedents that I report in 2014 could be due to period effects stemming from the different times we collected data.