In a market where past-sales embody information about consumers' tastes, we analyze a seller's incentives to invest in a costly advertising campaign to report past-sales. If consumers are poorly informed, a pooling equilibrium with past-sales advertising obtains. Information revelation only occurs when the seller benefits from the consumers' herding behavior brought about by the advertising campaign. If consumers are better informed, a separating equilibrium with past-sales advertising arises. Information revelation always happens, either through prices or through costly advertisements.
two-sided uncertainty; past-sales advertising; pooling; signalling; herding
