Prior-Free Clock Auctions for Bidders with Interdependent Values

07/20/2021

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by   Vasilis Gkatzelis, et al.

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We study the problem of selling a good to a group of bidders with interdependent values in a prior-free setting. Each bidder has a signal that can take one of k different values, and her value for the good is a weakly increasing function of all the bidders' signals. The bidders are partitioned into ℓ expertise-groups, based on how their signal can impact the values for the good, and we prove upper and lower bounds regarding the approximability of social welfare and revenue for a variety of settings, parameterized by k and ℓ. Our lower bounds apply to all ex-post incentive compatible mechanisms and our upper bounds are all within a small constant of the lower bounds. Our main results take the appealing form of ascending clock auctions and provide strong incentives by admitting the desired outcomes as obvious ex-post equilibria.