An arbitrageur with short investment horizon gains from accelerating price discovery by advertising his private information. However, advertising many assets may overload investors’ attention, reducing the number of informed traders per asset, and slowing price discovery. So the arbitrageur optimally concentrates advertising on just a few assets, unless his trades have significant price impact. The arbitrageur’s gain from advertising is increasing in the assets’ mispricing and in the precision of his private information, and is decreasing in its complexity. If several arbitrageurs have private information, inefficient equilibria can arise, where substantial mispricing persists or investors’ attention is overloaded.

In many environments, including credit and online markets, records about participants are collected, published, and erased after some time. We study the effects of erasing past records in a dynamic market where the quality of sellers follows a Markov process, and buyers leave feedback about sellers to an information intermediary. When the average quality of sellers is low, unlimited records lead to a market breakdown in the long run. We consider the information design problem and characterize information policies that can sustain trade and that maximize social welfare. These policies hide some information from the market in order to foster socially desirable experimentation. We show that these outcomes can be implemented by appropriately deleting past records. Crucially, positive and negative records play opposite roles with different intensities and must have different lengths: negative records must be deleted sufficiently late, and positive ones sufficiently early.