We extend Myerson's (1981) model by allowing for uncertainty about the number of bidders. In such extension the Revenue Equivalence Theorem still holds and the optimal allocation rule remains the same. Hence, the optimal auction can be implemented with an appropriate reserve price. Nonetheless,...

We show that open ascending auctions are prone to inefficient rushes, i.e. all bidders quitting at the same price, in market environments such as privatizations, takeover contests, and procurement auctions. Rushes arise when an incumbent with better information about a common value component of...