When bidders are not substitutes, we show that there is no standard ascend-ing auction that implements a bidder-optimal competitive equilibrium under truthful bidding. Such an impossibility holds also in environments where the Vickrey payoff vector is a competitive equilibrium payoff and is thus...

In the symmetric independent private value model, we revisit auctions with entry by adding two additional ingredients: difficulties to commit to the announced mechanism, in particular not to update the reserve price after bidders took their entry decisions, and seller's ex ante uncertainty on...

Brendstrup (2007) and Brendstrup and Paarsch (2006) claim that sequential English auction models with multi-unit demand can be identified from the distribution of the last stage winning price and without any assumption on bidding behavior in the earliest stages. We show that their identification...

We consider standard auction models when bidders' identities are not observed by the econometrician. First, we adapt the definition of identifiability to a framework with anonymous bids and we explore the extent to which anonymity reduces the possibility to identify private value auction models....

We consider the implementation of an economic outcome undercomplete information when the principal cannot commit to a simultaneousparticipation game. From a general class of sequential decentralizedparticipation processes and without common knowledge onthe details of the process, we introduce...

This comment nds an error in Cai, Riley and Ye [2] in presenceof informational externalities between bidders, the correction of whichgives a broader view on their comparative statics results with respectto n, the number of bidders. A linear specication of the informationalexternalities between...

The analysis of second price auctions with externalities is utterlymodied if the seller is unable to commit not to participate in themechanism. For the General Symmetric Model (Milgrom and Weber[20]) and standard auction formats, we charaterize the full set of symmetricpure strategy equilibria...

We consider standard auction models when bidders' identities arenot observed by the econometrician. First, we adapt the denition ofidentiability to a framework with anonymous bids and we explore theextent to which anonymity reduces the possibility to identify privatevalue auction models. Second,...

We introduce contingent auction mechanisms, which is a supersetof combinatorial auctions, and where bidders submit bids on packagesthat are contingent on the whole nal assignment. Without externalities,the Vickrey and the Ausubel-Milgrom Proxy Auction areboth robust if items are perceived as...