Tacit collusion, firm asymmetries and numbers: Evidence from EC merger cases

► We assess European Commission decision-making on mergers with coordinated effects. ► This sheds light on the conditions where tacit collusion is believed to arise. ► For the Commission tacit collusion is confined to markets of two symmetric firms. ► This is consistent with recent experimental literature. ► It contrasts with cartels where firm numbers and asymmetries are often larger.