We propose a new notion of credibility for Bayesian persuasion problems. A disclosure policy is credible if the sender cannot profit from tampering with her messages while keeping the message distribution unchanged. We show that the credibility of a disclosure policy is equivalent to a cyclical monotonicity condition on the policy’s induced distribution over states and actions. We also characterize how credibility restricts the sender’s ability to persuade under different payoff structures. In particular, when the sender’s payoff is state independent, all disclosure policies are credible. We apply our results to the market for lemons and show that no useful information can be credibly disclosed by the seller.

We investigate housing market distortions with the collusion of agents. The agency problem where agents sell clients' houses with price discounts while selling their own homes with price premiums is quite straightforward. However, the issue that agents collude with each other to further maximize their own interests is elusive. When agents collude, the resulting market distortions may even be worse than previous studies suggested. Indeed, this paper finds that the agency problem and market distortions are much more severe with agent collusion, as both the discounts associated with clients' houses and the premiums with agents' own homes become much larger when the two agents collude.