Is the U.S. Supreme Court That Divided and Political?

The National Review reports:

In recent reports, it’s been noted that 20 percent of the Court’s cases were decided 5–4 in the 2010 term. True, but 48 percent of the cases were decided 9–0, which reflects a pattern that has held for years. Is the Roberts Court any more divided than the William Rehnquist Court in 2000, when 30 percent of the cases were decided 5–4? Is the fact that Roberts and Alito agree 96 percent of the time really more troubling than the fact that Justices Elena Kagan and Sonia Sotomayor agree 94 percent of the time?