IIRC, this seems to imply companies are colluding. Does it even matter if it's tacit or explicit collusion? - Explicit collusion is hard to detect. Someone with interests (an exec with giant options and incentives), meets an Exec from another at dinner. They have a conversation. Who knows? - Implicit/Tacit collusion is easy. The execs know that they can defect (lower prices) as soon as they see the other party defect. Why would a potential competitor ever think arbitrary prices that could sink at any point would be a competitive advantage worth investing in?