On the Robustness of Second-Price Auctions in Prior-Independent Mechanism Design

Market designers often only have partial information about the environment and prefer simple mechanisms that are robust to the underlying uncertainty. In “On the Robustness of Second-Price Auctions in Prior-Independent Mechanism Design,” Anunrojwong, Balseiro, and Besbes study the fundamental problem of selling an item to n buyers, when only an upper bound on values is known and the seller minimizes worst-case regret. They establish that the same mechanism is robustly optimal across a wide range of environments for distributions of values: i.i.d., mixtures of i.i.d., exchangeable, and affiliated (the last two capturing positive dependence). Moreover, this robust mechanism is a second-price auction with random reserve price depending on n. Without positive dependence, the problem reduces to the one-buyer case. This result supports the wide use of second-price auctions in practice and allows them to quantify the robust value of competition in auctions.