In this paper I study two methods often used in public procurement to deal with the risk that the winning bidder may default on his bid: augmenting the standard first price auction with an ex-post verification of the responsiveness of the bids and using an average bid auction. I show that when...

We present an empirical investigation of the role of marketing agencies in Google's online ad auctions. By combining data on advertisers' affiliation to marketing agencies with data on bidding in ad auctions, we analyze how changes in the concentration of clients in the same industry under the...

As auctions are becoming the main mechanism for selling advertisement space on the web, marketing agencies specialized in bidding in online auctions are proliferating. We analyze theoretically how bidding delegation to a common marketing agency can undermine both revenues and efficiency of the...