The Supreme Court’s Divided Decisions

October 6, 2005

With the nomination of Harriet Miers to replace Justice Sandra Day O’Connor, long seen as a swing vote, the question of 5-to-4 divisions on the Supreme Court will loom large.

Many people think we live in an unprecedented era of remarkably close Supreme Court decisions. Don’t believe it. In the last three years, the court has decided 51 cases by a 5-to-4 vote. By historical standards, that’s not a large number. From 1998 to 2000, the court decided 61 cases by a 5-to-4 margin. From 1991 to 1993, the court so split in 53 cases. In the 1980s, 5-to-4 splits were even more common.

Percentages tell the same story as the absolute numbers. In the 1980’s, the court averaged more than 150 decisions each year. Under Chief Justice William Rehnquist, that number dropped until 1993; since then, the court has usually decided about 80 cases annually.

We might expect that if the court was taking fewer but perhaps harder cases, the percentage of 5-to-4 decisions would grow even if the total number did not. But the evidence does not support this speculation. In the 1980’s, when the court decided a large number of cases, 5-to-4 splits occurred 20 percent of the time. In the 1990’s, when the court decided many fewer cases, it split 18 percent of the time. In the last three years, about 21 percent of decisions have involved 5-to-4 splits, a figure well within historical ranges.

Why has the rate of 5-to-4 decisions remained relatively constant for so long? Is there a problem here? Senators from both parties have urged the court to make a serious effort to produce greater consensus.

These complaints reflect a misunderstanding of how the Supreme Court works. In fact, having a significant number of 5-to-4 splits is built into the court’s job.

One of the most important tasks of the Supreme Court is to resolve disagreements within the lower courts. In such cases, reasonable arguments will be available on both sides. So it should be no surprise if the Supreme Court’s members end up closely divided on the right answer.

More generally, the court manages its own docket; it takes cases only if it chooses to do so. No case will be heard unless at least four justices vote in favor of hearing it (the “rule of four”). Thus, the Supreme Court will become involved only if there is a good argument that the lower court was wrong. And if such an argument can be made, the case will probably be difficult and contentious, because lower courts usually offer plausible justifications for their rulings.

What would happen if presidents from the same party appointed all the court’s members? Would the number of 5-4 splits be diminished?

Almost certainly not. Both the law and the mix of cases brought in the federal courts would change, so as to reflect the new set of views within the court. But the court would continue to become involved only in the cases that would appear difficult to its members – those cases in which both sides could make reasonable arguments.

In short, on any court that consists of nine human beings, 5-to-4 splits are nearly inevitable—and they will probably occur about 20 percent of the time.