Nicolas de Roos (Sydney University) and Mathias Reyaert (Toulouse School of Economics) visited Mannheim to present their recent work on cartels in a series of MaCCI/EPoS seminars. Prof. de Roos discussed how price-comparison platforms can serve as facilitating devices, arguing that such platforms enable effective price signaling and thus allow cartel participants to coordinate on higher prices. Prof. Reyaert gave a talk on the recent AdBlue case, in which firms allegedly colluded against imperfectly monitored environmental regulation. Using a structural model of the European automobile industry, he argued that the collusion substantially lowered expected noncompliance penalties.