It is a core principle of antitrust law and theory that reduced market concentration lowers the risk of anticompetitive behavior. We demonstrate that this principle is fundamentally incomplete.Traditional models assume that firms interact only as competitors. We examine and model...

Many markets, including markets for IPOs and debt issuances, are syndicated: each winning bidder invites competitors to join its syndicate to complete production. Using repeated extensive form games, we show that collusion in syndicated markets may become easier as market concentration falls,...