An experimental approach is used to examine the performance of three different multiunit auction designs: discriminatory, uniform-price with fixed supply, and uniform-price with endogenous supply. We find the actual strategies to be inconsistent with theoretically identified equilibrium strategies. The discriminatory auction is found to be more susceptible to collusion than either uniform-price auction and so, contrary to theoretical predictions and previous experimental results, it generates the lowest average revenue. Consistent with theoretical predictions, the actual bid schedules are more elastic with reducible supply or discriminatory pricing than in the uniform-price auction with fixed supply.

We show that asymmetry in bidders' capacity constraints plays an important role in inhibiting collusion and promoting competitive outcomes in multi-unit auctions in which the final value of the good is common knowledge. This effect appears to be related to the increased difficulty of coordination when there are significant differences between bidders. Due to its impact on collusive outcomes, asymmetry in bidding capacities has a more powerful impact on the seller's revenue than does the auction type. Consistent with the finding in Sade et al. (2006) that the discriminatory auction is more susceptible to collusion than the uniform-price auction, asymmetry in capacity constraints has a greater impact in discriminatory auctions.

An experimental approach is used to examine the performance of three different multiunit auction designs: discriminatory, uniform-price with fixed supply, and uniform-price with endogenous supply. We find the actual strategies to be inconsistent with theoretically identified equilibrium strategies. The discriminatory auction is found to be more susceptible to collusion than either uniform-price auction and so, contrary to theoretical predictions and previous experimental results, it generates the lowest average revenue. Consistent with theoretical predictions, the actual bid schedules are more elastic with reducible supply or discriminatory pricing than in the uniform-price auction with fixed supply.