Collusive equilibria exist in open ascending auctions with multiple objects, if the number of the bidders is sufficiently small relative to the number of objects, even with large complementarities in the buyers' utility function. The bidders collude by dividing the objects among themselves,...

We identify and analyze three distinct effects arising from potentially binding budget constraints in multi-unit ascending auctions. First, binding budgets clearly reduce the level of competition among bidders. Second, budget constraints may at the same time make it difficult to sustain...