Jeffrey Segal recently updated the Segal/Cover perceived ideology scores by adding Samuel Alito. Alito rates a .1 on a scale that runs from 0 to 1.0, with 0 being the most conservative and 1.0 being the most liberal. The Court now lines up as follows:
These data and more, including
the perceived ideology scores for retired justices from Hugo Black (.875) to
Sandra Day O’Connor (.415), can be found at Professor Segal’s website.
For the details on this measure, see Lee Epstein & Jeffrey Segal, Advice and Consent 109-111 (Oxford 2005); Jeffrey Segal, Lee Epstein, Charles Cameron, & Harold Spaeth, "Ideological Values and the Votes of U.S. Supreme Court Justices Revisited," 57 Journal of Politics 812-823 (1995); Jeffrey Segal & Albert Cover, "Ideological Values and the Votes of U.S. Supreme Court Justices," 83 American Political Science Review 557-565 (1989).