Market Design and the Evolution of the Combinatorial Clock Auction

The Combinatorial Clock Auction (CCA) is an important recent innovation in auction design which has been adopted for many spectrum auctions worldwide. Since its inception, the CCA has been in almost continual evolution. We begin by reviewing some important changes which have already occurred. Despite these enhancements, we observe that the performance of the CCA is still limited by weak activity rules, suboptimal price feedback, and a missing-bid problem. We then describe further evolutionary changes, including new activity rules, new approaches to pricing, and an integration of non-mutually-exclusive bids, which will help to address these issues.