Market tallies: minimal information for efficient trade

This paper studies how much public information is needed to implement efficient trade in dynamic markets with privately informed sellers and buyers. An institution compares a certified statistic of market composition with the statistic implied by agents' reports. Truthful reporting is supported when the statistic changes after every unilateral change in reported type. When all market compositions are possible, the least number of public announcements is {K,L}, where K is the number of seller qualities and L the number of buyer types. The certificate must rely on information outside the reports it checks. The paper also shows that information sufficient to discipline reports need not coordinate buyers across limited capacity. Posted-price implementation may require certified capacities and a clearing rule.