ABSTRACT

Measuring ideology on the courts is important, yet challenging. This chapter discusses various approaches, ranging from calculating percent conservative scores to measures based on sophisticated measurement models, emphasizing two themes. First, scholars should not assume that all ideological measures work in all research contexts. I identify specific instances in which sophisticated measures produce questionable results. Second, ideology on the court is distinctive from ideology among elected officials, particularly on the Supreme Court, not only because justices are influenced by legal factors, but also because the small size of the Court makes the idiosyncratic world views of justices (and median justices in particular) decisive. The result is that the Court’s decisions may lack the ideological coherence more typically observed in Congress. While the task of measuring ideology on the Court may seem technical, it is in fact highly politically relevant and quite unsettled. The final part of this chapter explores the competing and evolving measures of ideology for the Roberts Court.