In Filibuster Shift, Focus on a Court's Workload and Political Balance WASHINGTON - The overhaul of the Senate's filibuster rules was prompted, surprisingly, by an argument about judicial productivity. Republicans said President Obama's nominees to three open seats on a federal appeals court in Washington were not needed because the court does not have enough to do. But trying to quantify the workload of the court, the United States Court of Appeals for the District of Columbia Circuit, "is a statistical food fight," said Russell Wheeler, an expert on the federal courts at the Brookings Institution. The real issue, he said, was "the ideological balance of the court." The court's eight current active judges are evenly divided between Republican and Democratic appointees. If Mr. Obama's pending appointments are confirmed under the new rules, which end the minority party's ability to filibuster most presidential nominees, that balance will change. But the court also has six semiretired judges, five of whom were appointed by Republican presidents. Their workloads vary, but on average they collectively handle the work of roughly three active judges, according to a letter in July from Chief Judge Merrick B. Garland to the Senate Judiciary Committee. That would more or less maintain an even balance when judges sit, as they typically do, on three-judge panels. But the semiretired judges generally do not sit when the full court reviews a panel decision, meaning that the court's Democratic appointees will have an edge. But will they use it? In remarks in April, Judge David S. Tatel, appointed to the court by President Bill Clinton, compared his voting record to that of Judge David B. Sentelle, who was appointed by President Ronald Reagan. "As it turns out, in the 19 years we've served together, we have disagreed less than 3 percent of the time," Judge Tatel said. Many of the cases on which Judge Sentelle and I have agreed are precisely the kind you would expect to divide us - and that would divide us if we were, heaven forbid, members of Congress: cases about greenhouse gases and global warming, military detention in Guantánamo and Afghanistan, constitutional claims to lifesaving drugs, the environmental consequences of nuclear waste, net neutrality, criminal law, tobacco and civil rights. That list is telling in two ways. It tends to confirm findings by political scientists that ideological voting is less common on federal appeals courts than on the Supreme Court. And it illustrates the breadth and importance of the District of Columbia Circuit's docket. It may also undercut the Republican critique that the court is underworked. As a matter of raw numbers, there is some support for the charge. But it fails to take account of the court's distinctive docket. "Comparing the number of cases it hears to other courts just doesn't work," said Eric M. Fraser, an author, with three colleagues, of a new study of the court's work to be published in the Cornell Journal of Law and Public Policy. Mr. Fraser is a former law clerk to Judge Douglas H. Ginsburg, who was appointed to the District of Columbia Circuit by Reagan. On the one hand, the study found, "a typical federal appellate judge may expect to participate in nearly three times the number of merits cases per year than a judge on the D.C. Circuit" - 168 versus 495 in a recent year, by one measure. On the other hand, Mr. Fraser said, "the types of cases and the types of opinions the court issues are very different." Tracey E. George, an expert on the federal appeals courts who teaches law and political science at Vanderbilt University, said assessing judicial productivity was hard. "It's obviously not as simple as counting cases," she said. If it were all about a court's cases, the U.S. Supreme Court has no work at all. The Supreme Court issues perhaps 75 signed decisions in argued cases each term, or about eight per justice. The District of Columbia Circuit hears fewer routine matters than other federal appeals courts and more technical ones, Mr. Fraser's study found. In particular, it hears many fewer criminal and commercial cases. More than half of its cases are administrative matters or suits against the federal government, compared to 20 percent nationwide, the study found. Many of those cases are sprawling and esoteric. This is partly because Congress authorized the District of Columbia Circuit to hear cases in more than 130 different laws. Some laws require direct appeals to the appeals court from regulatory determinations without a stop at a trial court. And it gives its cases more careful attention, hearing arguments more often and issuing a higher proportion of published decisions. The court's decisions fare well in the Supreme Court, which on average affirms them more often than those of other courts. The court is also a farm team for the Supreme Court. Chief Justice John G. Roberts Jr. and Justices Antonin Scalia, Clarence Thomas and Ruth Bader Ginsburg all served on it, and Justice Elena Kagan's nomination to it by President Bill Clinton stalled in the Senate. As a senator in 2005, Mr. Obama said all of this meant that nominations to the court warranted exceptional scrutiny. "This is a special court," he said, explaining why he was opposed to the nomination of Judge Janice Rogers Brown. It has jurisdiction that other appeals courts do not have. The judges on this court are entrusted with the power to make decisions affecting the health of the environment, the amount of money we allow in politics, the right of workers to bargain for fair wages and find freedom from discrimination, and the Social Security that our seniors will receive. Mr. Wheeler, of the Brookings Institution, said a "nonpartisan sober assessment" of the workloads of the federal appeals courts would be warranted and welcome. But, he added, "I'm not entirely sure what the right metrics are."