The Supreme Court has wide discretion to choose the cases it will decide. But how does the Court exercise this discretion? The Supreme Court’s rules explain that it may hear any case “important” enough for it to decide. Unsurprisingly, commentators have criticized this standard as “hopelessly indeterminate” and “intentionally vague.”

The Court, however, has said more about how it decides whether to grant review. We need simply to look to its merits opinions. These decisions sometimes offer a brief, informative description of the decision to grant review. These oft-overlooked statements may, in aggregate, be suggestive of trends in the Court’s agenda-setting discretion.

This Article presents a text and data analysis of thousands of Supreme Court opinions describing the reason for granting review, collectively illuminating which cases are important enough to merit certiorari. This view into certiorari helps reveal which cases earn the Court’s attention and how the Court’s priorities change over time. This analysis finds, for example, that the Court’s docket shifts in response to large events (e.g., depressions and wars) and to significant political developments (e.g., landmark legislation). And, perhaps more concerning, individual appointments also shape the Court’s docket. The Court should thus better explain its decisions to grant review in the mode of a common law of certiorari. Doing so can improve the interbranch dialogue over judicial reform, offer better information to litigants, and instill greater confidence in our Supreme Court.