Preserving Bidder Privacy in Assignment Auctions : Design and Measurement

Motivated by bidders' interests in concealing their private information in auctions, we propose an ascending clock auction for unit-demand assignment problems that economizes on bidder information revelation, together with a new general-purpose measure of information revelation. Our auction uses an iterative partial reporting design such that for a given set of prices, not all bidders are required to report their demands, and when they are, they reveal a single preferred item at a time instead of all. Our design can better preserve bidder privacy while maintaining several good properties: sincere bidding is an ex-post Nash equilibrium, ending prices are path independent, and efficiency is achieved if the auction starts with the auctioneer's reservation values. Our measurement of information revelation is based on Shannon's entropy and can be used to compare a wide variety of auction and non-auction mechanisms. We propose a hybrid quasi-Monte Carlo procedure for computing this measure. Our numerical simulations show that our auction consistently outperforms a full-reporting benchmark with up to 18% less entropy reduction, andscales to problems of over 100,000 variables