We conduct an experiment on voluntary disclosure within a simple bargaining setting wherein a proposer must choose one of two possible offers and a responder chooseswhether to reject or accept that offer. In one treatment the proposer has the option to disclose whether a fairer (more equal) offer was available relative to the one chosen. Understandard economic theory, a responder will interpret no disclosure to mean the proposer’ soffer was the less fair alternative, and so a proposer who is making the fairer offer will dis-close. In consequence, voluntary disclosure should perform as well as mandatory disclosurein motivating proposers to make fair offers. Given their rejection rates, we find respondersproperly infer the meaning of non-disclosure. However, despite the correct inferences madeby responders, proposers submit twice as many fair offers with mandatory disclosure than with voluntary disclosure. Our results suggest that the choice of voluntary versus mandatory disclosure has consequences for resource allocation within the firm even though understandard assumptions about preferences it should not.