In this paper, we propose a perfect competition test which checks whether arbitrarily small coalitions of firms, which behave strategically on costs, are able to manipulate prices in their own benefit. We apply this test to economies with a continuum of differentiated producers. We show that,...

In this paper we consider sequential second-price auctions where an individual's value for a bundle of objects is either greater than the sum of the values for the objects separately (positive synergy) or less than the sum (negative synergy). We show that the existence of positive synergies...

We study endogenous-participation auctions where bidders only know the number of potential participants. After seeing their values for the object, potential participants decide whether or not to enter the auction. They may not want to enter the auction since they have to pay participation costs....