Shill bidding in online English auctions with a random number of bidders

Shill bidding has increased substantially with the explosion in the number of online auctions. For English auctions with conventional intermediation fee schedules and a continuous increment of the bid, sellers may profit from shill bidding, which is illegal. To deter shill bidding, Wang et al.(31) designed a mechanism - the shill-deterrent fee schedule (SDFS) which makes shill bidding unprofitable. This paper analyzes the feasibility of applying SDFS rules to both single round and multi-round English auctions in a framework of independent private value (IPV) with a random number of bidders. It is shown that most of the results in Wang et al.(31) remain true at our cases. In addition, we also propose an approach for sellers to reset the subsequent reserves in multi-round English auctions.