Auction cartels and the absence of efficient communication

This paper examines the feasibility of collusive mechanisms in single-unit auctions. A model is constructed with private and common value information asymmetry and continuous type space. We show that an incentive compatible bid coordination mechanism (BCM) does not exist if common value uncertainty is present. This result contradicts actual antitrust cases, where common effects or resale opportunities created uncertainty about valuations, but a price-fixing cartel was formed. We solve the puzzle by relaxing the assumption that all bidder types truthfully reveal their private information. The introduced Bayesian bid coordination mechanism (BBCM) exists if the main source of information asymmetry is private value. In that case, a designated ring member can signal high valuation and suppress competition. Our results demonstrate the rationale behind cartel mechanisms with pre-auction knockouts.