Nope, Sorry, Supreme Court Justices Aren't Staying on the Bench Longer

This is not the post I expected to write. I expected to write a post offering an alternate interpretation of the statistics in this Slate post advocating an attack on life tenure for federal judges. Basically, they present data showing that more Justices are staying on the Court at least 10, 20, and 30 years since 1900 than did so before that year. My argument was going to be that this wasn't necessarily because the Justices were living longer, but just that the Supreme Court has come to be seen as a more important institution, basically as constitutional law and individual-rights law have grown to their current prominence, and so fewer Justices were just leaving to go do something better. I was going to claim that you could see this in the massive increase of 10-year Justices, and the proportionally similar growth of 20-year ones, and the complete lack of an increase in 30-year Justices. But, as it happens, I'm not going to write that post. Because while I was writing that post I discovered that I couldn't generate their numbers for myself, by looking at the very-publicly-available and not-very-complicated data. In fact they don't state very explicitly how they're getting their numbers, and I can make one assumption that gets me numbers close to theirs, though not the very same numbers. But that's not really my point, I don't care much about whether someone writing a Slate post got slightly wrong how long the various Justices have been in office. No, my point is that my own look at the data suggests that their factual conclusion is just wrong: there has been no long-term trend toward longer terms in office among Supreme Court Justices, though there's some reason to think the current Court might be beginning to exhibit one. The data here is really tricky, but I'll go through it in some detail below the jump.


First, the discrepancy. They say that, "Before 1900:

• 26 justices served 10 years or more
• 18 justices served 20 years or more
• 7 justices served 30 years or more

"Whereas since 1900:

• 48 justices have served 10 years or more
• 27 justices have served 20 years or more
• 8 justices served 30 years or more"

Now, my initial assumption was that since they described these numbers as being "based on an analysis of more than two centuries of Supreme Court appointments," they were grouping Justices by date of appointment, before or after 1900. When I went through and looked at the 112 Supreme Court Justices that there have been, however, 57 of whom were appointed before that line and 55 of whom after it, I found veeery different figures. Specifically, for the pre-1900 group I got 38 in the 10+ bucket, 23 in the 20+ ring, and 8 Justices who stayed for at least 30 years, leaving 19 Justices who didn't last a decade. On the post-1900 side I got 36 in the 10+ column, 20 in the 20+ column, and just 6 30+ Justices, with an identical 19 serving less than a decade. (Note, however, that those numbers include the incumbent Justices, four of whom haven't been there for a decade yet but presumably will be.) Those look, well, not so different. Interestingly, the average tenures for Justices appointed before and after 1900 look awfully similar: 6,084 days in office for the former group, 6,056 days for the latter. Spot the difference? Me neither. If I exclude incumbent Justices from the second group, that figure jumps all the way to 6,146, which is a difference of two months over the nineteenth-century figure.

There's another way to look at it, however, and that's to sort the Justices by their date of retirement or death, rather than by date of appointment. For reasons I'll get to in a bit I think this is a less honest way to slice the data, but it also seems like they might have using it. In any event, I still don't get their numbers. Of the 48 Justices who left the Court prior to the year 1900, I find 29 who lasted at least a decade, 17 who lasted at least two decades, and 7 who lasted at least three decades. Those are very similar to their figures, though not exactly the same, and I can't really reconcile the discrepancies by assuming anything about rounding errors or whatever. Of the 55 Justices who have left the Court but hadn't done so yet by 1900, I find that 40 served at least a decade, 22 served at least two decades, and  7 lasted at least three decades. Of the nine who haven't ever left the Court, i.e. the incumbent Justices, five have been there at least a decade, of whom only one hasn't been there at least two decades, while none have yet made it to the thirty year mark. (If Scalia and Kennedy don't, however, Obama will get to replace them.) So... measured this way there does seem to be a bit of a shift toward longer terms. Indeed, the average time on the bench for those who left before 1900 was 5,778 days, while the average for those who retired some time between 1900 and 2012 was 6,403 days. That looks like a slightly more meaningful increase, nearly two years on average.

Except I think there's a problem with sorting by retirement date and then drawing a dividing-line: your selection criteria incorporates information about how long a Justices managed to stay on the bench. That is, two Justices appointed in 1880 will fall in different buckets if one of them stayed on the Court for 25 years but the other one stayed for only 15. That prejudices the numbers, putting more long-tenured Justices into the post-1900 bucket by design. There are nine Justices who were appointed before 1900 but retired after that date, not surprisingly since they were the nine incumbents during 1900 itself. They averaged 7716 days on the bench. They were appointed during the window from 1877 to 1898. During that same span, five Justices were appointed who didn't make it to the twentieth century. They averaged 2404 days on the bench. All fourteen Justices appointed during these years averaged 5819 days in office, similar to the long-term average. The discrimination here is staggering. If this is how they got their numbers, which are in any event not exactly the numbers I get, they had to effectively cherry-pick a group of very long-lasting Justices out of the nineteenth century and drop them down in the twentieth-century bucket to get any sort of apparent result.

So their numbers are wrong, and while you can use one method that makes them almost not wrong, that method is an extremely unsound one. More interesting to me is that there just hasn't been any long-term trend toward longer stays on the Court. This is not what you hear, and it's certainly not what the people advocating a reform of life tenure want you to hear. Now, this approach paints with a very broad brush, dividing all the Justices into two big categories. So I broke things down a little further, dividing up the 103 former Justices into four buckets based on 50-year windows in appointment date, and took the average for each bucket. Here's what I found: the Justices appointed from 1789 to 1839 stayed an average of 6131 days; those appointed from 1840 to 1889 stayed an average of 6033 days; those appointed from 1890 to 1939 stayed an average of 6189 days; and those appointed from 1940 through 1990, when David Souter, the most-recently-appointed former Justice, was appointed, lasted an average of 6072 days. There's no trend. None. And if you try to break it down much further, the sample sizes start getting a bit small; if I used, say, eight buckets of 25 years apiece, they'd each have only 12 or 13 Justices in them on average.

I will say in the spirit of full disclosure that Justices appointed from 1940 through 1964 lasted just 4950 days on average, while those appointed from 1965 through 1990 for whom we have final figures lasted a whopping 7943 days. And this is probably behind the sense that life tenure has gotten out of hand recently: we had a spate of extremely long-tenured Justices in a row, and the five older current Justices are all well above the historical average at this point, all of this coming after a period of uncommonly rapid turnover. But there's a reason sports types talk about small sample size: stuff happens. It may be that we've entered a new era where 8000-day terms have become the norm, or it may be that we've just been on a "hot streak" of Justices staying a long time, having been in a major slump right beforehand. Given the overall consistency of the 6000-day average, it's pretty likely that we'll revert to that mean over the next half-century. It wouldn't be that surprising because it's happened before. This post-1965 group includes just nine Justices. If I look at every window of nine consecutively-appointed Justices and take their average time in office, I find that we hit 8500 twice in the early Republic, and that overall the fourteen Justices appointed from 1799 through 1836, Bushrod Washington through Roger Taney, lasted 8345 days on average, and that includes three who didn't last 2000 days. Conversely, the first nine Justices appointed lasted just 3295 days on average, and the group of nine starting with James F. Byrnes (who skews things because he left after a year and a half, but them's the data) stayed just 3990 days on average. The point is, these variations happen, and just because, for instance, the fourteen Justices starting with William Brennan who've retired lasted around 7500 days on average doesn't mean that anything underlying has changed.

It is worth noting, however, that the current Justices seem well-positioned to continue the trend of longer tenures. Five of the Justices have already stayed at least 7000 days, with Scalia closing in on 10,000. That's five who've clinched exceeding the long-term average, in other words. And the other four were appointed within the last decade. They're also relatively young, with Samuel Alito at 63 the oldest of that bunch. So if those four stay for a long time, the current Court may turn out to have been one of exclusively long-lasting Justices, as the Courts of the seventies and eighties were. But we don't know that that will happen, and even if it does we don't know the trend will continue.

So, to sum up: at any reasonable scale of measurement there is no long-term trend toward Supreme Court Justices staying on the Court longer than they used to. However, the past three or four decades seem to have been different, and it remains to be seen whether something underlying has truly changed or whether we've just had a run of Justices who've stuck around forever. Given how recent the change was, even if it was real, however, and the fact that it came on the heels of a period of unusually short stays on the Court, it seems somewhat unlikely that improved medical technology is the culprit. In any event it seems a little bit of an overreaction to launch an assault on the central defining feature of the federal judiciary, its life tenure, because of what may turn out to be nothing more than a quirk of random distribution.