This paper analyses the optimal combination of costly and costless messages that a Sender uses in a signaling game if he is able to choose among all equilibrium communication strategies. We provide a complete characterization of the equilibrium that maximizes the Sender's ex ante expected...

Combinatorial Clock Auctions (CCAs) have recently been used around the world to allocate spectrum for mobile telecom licenses. CCAs are claimed to significantly reduce the scope for gaming or strategic bidding. This paper shows, however, that CCAs facilitate strategic bidding. Real bidders in...