In a follow-up to the work I've co-authored on Term Limits for Supreme Court Justices, I've been looking at the effects of any US Supreme Court retirements on the overall age and tenure distribution on the Supreme Court.
Many people assume that, if a Democrat wins the White House in 2008, there might be one or more resignations from the more liberal half of the Court in 2009 or 2010. Although it might seem that the oldest member of the Court, Justice John Paul Stevens (age 87), would be the likeliest to step down, those with better sources of information than I have say that Justice Stevens is still extremely bright and funny and appears to outsiders to be in excellent health. Since physically and mentally he appears to be going very strong, some observers have speculated that Justice Stevens may well stay on the Court at least until he breaks Justice Douglas's record as the longest serving Justice in the summer of 2012.
(I confess that I am happy to hear how well Justice Stevens is doing since, partly for personal reasons, Stevens is my favorite sitting Justice. Beyond his general brilliance, he has written by far the best opinions in an area of my scholarly interest, extortion law, and he has personally been the kindest Justice to me both privately and (from what I've been told) in public comments. By the way, my next favorite would come from the conservative wing of the Court.)
Among the other Justices roughly on the liberal side on the Court, Justices Ruth Bader Ginsburg and David Souter are being talked about as possibly retiring or taking senior status if a Democrat wins the White House. Justice Ginsburg, who is 74, strikes some observers as somewhat frail in comparison with other members of the Court. As to Justice Souter, there would be no particular reason for Souter to consider leaving the Court anytime soon, but his natural modesty may lead him to find retirement attractive in a few years, having already exceeded both the 1790-2006 mean (16.2 years) and median (15.3 years) terms on the Court.
In 2005, political scientist Kevin McGuire had falsely [i.e., incorrectly] claimed in print that if Justices O'Connor and Rehnquist left the Court (as they soon did), the median current tenure on the Supreme Court would drop to normal levels. Since in any given year the median justice would tend to be just past the mid-point of his judicial tenure on the Court, the median years of service in any given year has historically been about 9.2 years. (The median years of eventual tenure on the bench has been 15.3 years.)
The median tenure on the 2005 Court just before Chief Justice Rehnquist died was 17.5 years. After Justice Alito joined the Court at the end of January 2006, the median did not drop to the historical norm of around 9 years, but rather only to 14.3 years. So McGuire was wrong. Except for a few months in 1937 (when the median tenure of the then-sitting justices reached 14.4 years), these few months in early 2006 were still the highest median years of service on a current Court from the 1870s through the 1970s.
Now, a year and a half later, the median tenure on the Court has increased to 15.7 years. If there are no retirements until the summer of 2009, the median tenure will grow to 17.7 years, above even the level just before C.J. Rehnquist died.
As for other measures, the last nine Justices to leave the Court were (on average) about 79 years old when they left the Court and had spent about 25 years on the bench, both well above historical norms and slightly higher than at any time in history before the 1980s.