After the appointments of John G. Roberts and Samuel A. Alito, commentators were quick to point to a new source of diversity on the U.S. Supreme Court: religion. For the first time in the Court’s history, Protestants do not hold a majority or plurality of seats; Catholics do.

But religion may be the exception. On many other dimensions, the Roberts Court, as it is currently composed, is among the more homogeneous Courts in recent memory. Most noticeably, for the first time in American history all nine Justices came to their positions directly from U.S. courts of appeals.

While this “professionalization” of the Court is without precedent, it has been long in coming. Ever since President Dwight D. Eisenhower made clear that he “would use an appeals court appointment as a stepping stone to the Supreme Court,” the vast majority of nominees have come from the federal circuits. Even more to the point, the Senate has not confirmed any Supreme Court nominee lacking circuit court experience since William H. Rehnquist in 1986. Of course, there was President George W. Bush’s attempt in 2005 to appoint his White House counsel, Harriet Miers. Ironically enough, this nomination—so roundly criticized on the very ground that Miers had never served on the bench—may have solidified the practice of looking to the circuits for Supreme Court nominees. As one observer noted, “[t]he appointments of Chief Justice Roberts and Justice Alito, and contrastingly the rejection of Harriet Miers, reinforce a trend on the Court that nominees not only have prior judicial experience, but also federal appellate experience.”

Circuit Effects: How the Norm of Federal Judicial Experience Biases the Supreme Court