Existing scholarship on US Supreme Court certiorari has largely centered on the demand side, prioritizing the internal motivations of justices. This approach often overlooks the broader supply-side perspective—the nature and evolution of the complete pool of petitions. This study addresses this gap by analyzing the universe of writs of certiorari from 1946 to 2019. Coding for petition date and origin, petitioner identity, and disposition, we trace the composition of petitions across eras and jurisdictions. By linking petitions to merits-stage attributes, we find that the Court’s plenary docket is selected from a geographically and organizationally uneven petition environment, that federal-origin petitions dominate both filings and the docket, and that institutional repeat players succeed at higher rates than individuals despite a steady increase in petitions from the latter. By mapping this upstream landscape, we provide a descriptive baseline and measurement framework that illuminates the dynamics of the petition supply and provides context to the demand-side accounts of Supreme Court agenda-setting.

The majority opinion of the Supreme Court establishes precedent, but separate opinion writing affords the justices the ability to expound upon it or express their disagreement with the ruling or its logic. We broaden the exploration of separate opinion writing to consider how decisions and case features at the moment of granting cert shape justices’ decisions to engage in nonconsensual behavior. We also sharpen the focus on external actors to consider the nature of amici curiae. Through an empirical study of Supreme Court cases between 1986 and 1993, we find that aspects of the agenda-setting stage affect justices’ decisions at the litigation stage. In addition, we find that the number of briefs and the diversity of organized interests impacted by the case is particularly relevant to justices. The decision to write a separate opinion is the product of internal and external factors over the full course of a case’s history.