The German 4g Spectrum Auction: Design and Behaviour*

The 2010 German 4G spectrum auction was an unusually large simultaneous ascending multi-band auction. The bidding was competitive and the final assignment was efficient. However, our analysis suggests that independent and rational bidders had an opportunity to coordinate implicitly on a lowrevenue outcome. Coordination was difficult, though, because of a multiplicity of focal points. One important focal point involved post-auction negotiations, posing risks to bidders and the auctioneer. We analyse different bidding scenarios and how post-auction negotiations can affect values, bidding and efficiency. We also discuss how the simultaneous ascending auction format can be augmented to mitigate the risks.