Unobserved collusion: Warning signs and concerns: Keynote address at the antitrust enforcement symposium, June 2017

In a keynote speech Robert C. Marshall addresses unobserved collusion. Although the extent and scope of unobserved collusion is unknown, the repeated detection of cartels among some multi-product firms raises questions and concerns. Do some multiproduct firms potentially have a large portfolio of cartels where detected cartels are just a small part of their total collusive activity? This address examines conduct by multi-product firms that suggests potential grounds for concern.