Measuring the relative location of U.S. Supreme Court justices on an ideological continuum allows us to better understand the politics of the high court. In addition, such measures are an important building blocking of statistical models of the Supreme Court, the separation of powers system, and the judicial hierarchy. This website contains the so-called "Martin-Quinn" measures of judicial ideology developed by Andrew D. Martin (University of Michigan, College of Literature, Science, and the Arts) and Kevin M. Quinn (Department of Political Science, University of Michigan).

The "Martin-Quinn" scores are estimated for every justice serving from the October 1937 term to the present. Currently estimates are available through the October 2016 term.

The measures are estimated using a dynamic item response theory model, allowing judicial ideology to trend smoothly through time. The animated figure above demonstrates these dynamics. Since the scores are estimated from a probability model, they can be used to form other quantities of interest, such as locating the pivotal "median" justice, as all well the location of each case in the policy space.

icnNsf.gifThis material is based upon work supported by the National Science Foundation under Grants SES-01-35855 and SES-01-36679, the Center for Empirical Research in the Law at Washington University. Neither the National Science Foundation, Washington University, nor the University of Michigan bear any responsibility for this content.