Contrary to conservatives' claims that the Supreme Court under Chief Justice John Roberts is a moderate court, The New York Times reports that, according to “an analysis of four sets of political science data,” the Roberts Court has become “the most conservative one in living memory.” From the July 25 Times article:

When Chief Justice John G. Roberts Jr. and his colleagues on the Supreme Court left for their summer break at the end of June, they marked a milestone: the Roberts court had just completed its fifth term.

In those five years, the court not only moved to the right but also became the most conservative one in living memory, based on an analysis of four sets of political science data.

And for all the public debate about the confirmation of Elena Kagan or the addition last year of Justice Sonia Sotomayor, there is no reason to think they will make a difference in the court's ideological balance. Indeed, the data show that only one recent replacement altered its direction, that of Justice Samuel A. Alito Jr. for Justice Sandra Day O'Connor in 2006, pulling the court to the right.

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Analyses of databases coding Supreme Court decisions and justices' votes along these lines, one going back to 1953 and another to 1937, show that the Roberts court has staked out territory to the right of the two conservative courts that immediately preceded it by four distinct measures:

In its first five years, the Roberts court issued conservative decisions 58 percent of the time. And in the term ending a year ago, the rate rose to 65 percent, the highest number in any year since at least 1953.

The courts led by Chief Justices Warren E. Burger, from 1969 to 1986, and William H. Rehnquist, from 1986 to 2005, issued conservative decisions at an almost indistinguishable rate -- 55 percent of the time.

That was a sharp break from the court led by Chief Justice Earl Warren, from 1953 to 1969, in what liberals consider the Supreme Court's golden age and conservatives portray as the height of inappropriate judicial meddling. That court issued conservative decisions 34 percent of the time.

Four of the six most conservative justices of the 44 who have sat on the court since 1937 are serving now: Chief Justice Roberts and Justices Alito, Antonin Scalia and, most conservative of all, Clarence Thomas. (The other two were Chief Justices Burger and Rehnquist.) Justice Anthony M. Kennedy, the swing justice on the current court, is in the top 10.

The Roberts court is finding laws unconstitutional and reversing precedent -- two measures of activism -- no more often than earlier courts. But the ideological direction of the court's activism has undergone a marked change toward conservative results.

Until she retired in 2006, Justice O'Connor was very often the court's swing vote, and in her later years she had drifted to the center-left. These days, Justice Kennedy has assumed that crucial role at the court's center, moving the court to the right.