Since the introduction of spectrum auctions in 1994, the FCC has introduced rule changes including click box bidding, presence of large minimum opening bids and anonymous bidding that potentially make collusion more difficult. Click box bidding makes it harder for bidders to directly signal each other. Large minimum opening bids give bidders fewer rounds for communication via bids to work out a split of the licenses before prices become too high. Anonymous bidding disguises the identity of bidders during the auction, making it di¢ cult, and perhaps impossible, for the cartel to use the bids to monitor and enforce collusive agreements.