In this chapter we will attempt to ascertain some of the characteristics of the overruling and overruled cases. Although we will mainly examine the overruling and overruled cases themselves, at times we will also compare these cases with the non-overruling and the non-overruled cases. We will both present descriptive data and test hypotheses.

THE AGES OF THE OVERRULED PRECEDENTS

As we indicated in Chapter 2, Ulmer discovered that the Supreme Court's 11- to 20-year-old decisions were more likely to be overruled than those of any other age. He also found that only 3 percent of the overturned precedents exceeded 95 years of age. Blaustein and Field, whose study covered the Court through the 1956 term, found that the mean life-span of overruled cases was 24 years and the median life-span was 17 years.

We inspected the ages of the 154 overruled precedents of our study and discovered that the most frequently overruled decisions were 0 to 10 years old (26.6 percent), followed by those decided 11 to 20 years previously (23.4 percent). (See Table 4.1.) In other words, half the overruled decisions survived less than 21 years. (Ulmer's comparable proportion is 64 percent.) We also found that 6.4 percent of the overturned cases (10 cases) were over 90 years old. (Ulmer's comparable figure is 3 percent, or 3 cases.)

The conventional wisdom does not specify an age at which precedents become sacrosanct. Nonetheless, we certainly feel safe in assuming that cases decided in the nineteenth century and earlier qualify in this regard. Inspection of the list of overruled decisions in Appendix I shows that slightly more than 10 percent of them predate 1900 (16 of 154).