Misbehavior in Common Value Auctions: Bidding Rings and Shills

We characterize the optimal misbehavior by bidding rings or an auc-tioneer in the ascending English auction with common values. We also show, in an extended game, that in equilibrium potential members join and truthfully reveal their signals. Under a separability assump-tion, behavior does not change if nonring bidders are informed about the ring's existence. In general, misbehavior in dynamic settings is more profitable than in outcome-equivalent static settings. However, under a stronger separability assumption, the ring can do no better in the dynamic English format than in the outcome-equivalent, static Sophi format.