Supreme Court Breakfast Table

Why Does the Supreme Court Decide Most Cases Either 9–0 or 5–4?
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July 1 2014 11:07 AM

Supreme Court Breakfast Table

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Why does the court usually decide cases either 9–0 or 5–4?

Supreme Court Ruling
A journalist runs out of the Supreme Court on June 30, 2014, carrying a copy of the decision in the Hobby Lobby case, yet another 5–4 ruling.

Photo by Chip Somodevilla/Getty Images

As Larry mentioned (and see Walter’s contribution earlier today), the court delivered a surprising number of unanimous opinions in its last couple of weeks, when normally the most controversial cases are decided. Neal Katyal, writing in the New York Times, celebrates the unusually large number of unanimous opinions that were issued over the entire term. Katyal fulsomely credits Chief Justice John Roberts for the “modesty and cultivated collegiality” of the justices, calling them a model for the rest of government, which seems to be caught up in an endless blood feud. He contrasts Robertsian harmony with then-Chief Justice William Rehnquist’s “exasperation at the fractured court” in 2005. Larry is less impressed because the separate opinions in some of the unanimous cases reveal significant disagreement. Scalia’s ominous statement in McCullen that “I prefer not to take part in the assembling of an apparent but specious unanimity,” suggests if nothing else that Scalia will need some polishing before he will be able to take his place among Katyal’s judicial Teletubbies.

So what’s the truth about unanimity on the court? Katyal is wrong to say that the long-term decline in fragmentation is due to Roberts. As you can see from the table here, which I compiled from data from Scotusblog, the current fraction of 9–0 and 5–4 opinions has not changed much, overall, since 1995. That is midway through Rehnquist’s tenure; Roberts did not join the court until 2005. The fragmentation was higher if you go back to the 1980s and before. Why exactly it declined in the 1990s is unclear, but if credit should go to anyone, it should go to Rehnquist, who was well-liked by the other justices. It is also possible that random shifts in the composition of the court mattered more than anything the chief justice did.

140701_BFAST_VoteSplitGraph

We are left with a couple of puzzles. One is why the number of 9–0 opinions was so much higher this term than in the earlier terms under Roberts’ tenure. I don’t know the answer, but I suspect this is just random variation. The table shows a lot of variation over the years.

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Another odd feature of the data is that the court achieves unanimity a great deal of the time, and divides 5–4 quite often, but hardly ever divides 8–1, 7–2, or 6–3. (You can’t see this in the table, but it’s true.) To see why this is strange, imagine that (as it is often said) the cases that the court takes are very hard. Then you would expect the justices to disagree a great deal of time. You’d see a lot of 5–4s, slightly fewer 6–3s, 7–2s, and 8–1s, and hardly any 9–0s. Or if you think the court for some reason takes easy cases, then you’d expect lots of 9–0s, slightly fewer 8–1s, and so on, and hardly any 5–4s. If the court takes easy and hard cases, there should still be many 8–1s, 7–2s, and 6–3s.  Instead, the vote divisions follow a U-shaped curve, with many 9–0s and many 5–4s, and hardly anything in between.

Why? Many of the court’s cases don’t divide along ideological lines. The justices probably don’t bother to express their disagreements in cases when less is at stake ideologically. They don’t care, or they think that the (false) appearance of agreement enhances the court’s image. When a case does raises ideologically charged questions, the justices split along the predictable lines.

It’s often said the court should avoid disagreements because disagreement undermines its authority. But the real problem is not disagreement—reasonable people will always disagree about hard cases. The real problem is ideological disagreement. When the Republican-appointed justices and the Democratic-appointed justices divide 5–4, we suspect that they are not doing law but politics. But even when all nine justices agree on the outcome, that outcome can be—and likely is—determined by an ideologically driven compromise that takes place in the justices’ chambers, as Scalia’s comment about specious unanimity suggests. Contrary to Katyal’s argument, unanimity may mask ideology rather than show its absence. Thus, the accomplishment for Roberts (and for Rehnquist) is not to reduce the role of ideology in decision-making, but to suppress the visible evidence of ideological disagreement. That’s an accomplishment of tactical skill, to be sure, but nothing to celebrate. And it has hardly worked for buffing the court’s reputation: Confidence among the public in the Supreme Court reached a record low this year, far lower than the bad old days of the 1970s and 1980s.

Eric Posner, a professor at the University of Chicago Law School, is author of The Twilight of International Human Rights Law. Follow him on Twitter.