This Essay was prepared for the symposium organized by The University of Chicago Law Review on Reassessing the Chicago School of Antitrust Law, held on May 10–11, 2019. We thank the participants of the symposium for helpful feedback. Special thanks also to Patrick Todd for illuminating conversations. We are indebted to the over one hundred research assistants at Columbia Law School and The University of Chicago Law School that helped us gather and code the antitrust data we employ in this Essay. Our thanks also to the antitrust enforcers in the 103 agencies that generously provided information for this study. We gratefully acknowledge the funding by the National Science Foundation that supported the early data gathering effort (see NSF-Law & Social Sciences grants 1228453 & 1228483, awarded in September 2012). The coding was subsequently expanded with the generous support of the Columbia Public Policy Grant: “Does Antitrust Policy Promote Market Performance and Competitiveness?,” awarded in June 2015, and additional financial support from Columbia Law School. We also thank the Baker Scholars fund at The University of Chicago Law School for financial support. Except as otherwise noted, all data is available at the Comparative Competition Law Project website, http://comparativecompetitionlaw.org.