The Supreme Court can deal with eight justices

Being reduced to eight Supreme Court justices after the death of Antonin Scalia doesn't necessarily mean the court is doomed to months of unproductive gridlock.

In fact, an evenly split court really isn't anything new. As Justice Samuel Alito pointed out last week, the court has had an even number of justices in the past. Nearly 1 in 5 decisions passed down since 1946 were decided by an even number of votes, according to a CNBC.com analysis.

Evenly split courts, which are usually caused by a recused justice or a temporary empty seat, are common, making about 19 percent of all decisions. Yet only 5 percent of those decisions have been ties, suggesting that most courts manage to secure a majority one way or another.

According to the historical data back to 1946 from the Supreme Court Database, there have been no tied cases since 2010, despite more than 20 even courts.

Some of the prominent peaks in the chart seem to be caused by gaps between when a seat opened up and when a new justice was sworn in.

That happened during the 1969 term, which included cases decided in the gap between when Chief Justice Earl Warren retired in June 1969 and Harry Blackmun was sworn in a year later. During that period, 111 out of 141 cases were decided by an even court and only two ended up as ties — not bad for an even court.

At other times, an eight-person court has been caused by justices recusing themselves when they have a possible conflict of interest.

Thurgood Marshall removed himself from about 40 percent of the cases decided in his first term because he was solicitor general before being nominated. For the same reason, Justice Elena Kagan recused herself from dozens of cases after her 2010 nomination. At other times, justices did not participate in a series of cases due to illness.

Yet duringl those periods, the court has continued to turn out decisions. In 2005, none of the 23 decisions by even courts was a tie, and in 2010 only two out of 33 were. Even with an even court, about 40 percent of cases are decided unanimously.

If the court ties, the lower court's ruling stands. That indecision can lead to a split between the federal circuit courts, an outcome that the justices are keen to avoid, said Lee Epstein of Washington University in St. Louis, one of the principal investigators for the Supreme Court Database.

"They can leave the law even murkier than it was before with a 4-4 split, so they work hard to minimize them," Epstein said.

The court is not polarized enough to return a high number of ties, and if it is heading towards a tie the court has a lot of options to stop that from happening. Justices can write narrower opinions that they can agree on or they can order rearguments, effectively kicking the can down the road until a full court can lead to a decisive vote. Some justices may vote strategically to prevent a tie.

The end result is far fewer ties than statistics would suggest. And that hasn't changed much; the percentage of even court cases that are ties is about the same today as it was in the 1950s and 60s.

In fact, according to Epstein's calculations, the Roberts court has been the least likely to turn in ties out of the last four courts. Only 4 percent of even courts ended in ties, compared with about 7 percent of Rehnquist, 6 percent for Burger and 5 percent for Warren.