Antitrust populists increasingly call on the government to “break up big tech.” But antitrust enforcers would face heavy evidentiary burdens if they sought to break a company up on the premise that a long-consummated merger was unlawful from the outset and should have been blocked years ago....

Critics from both the right and the left claim that modern antitrust doctrine, rooted in consumer welfare, is inadequate to handle the challenges of the twenty-first century economy. They express nostalgia for 1960s antitrust, when the field had no clear objectives and cases were decided on...

This symposium began with a call for papers “re-assessing the validity of the Chicago School’s assumptions about competition and considering whether a more aggressive approach to antitrust enforcement is now warranted.” That framing uncritically accepts the premises of antitrust’s new...