This paper shows the experimental results for multi-object auctions in terms of efficiency, revenue, and bidders' payoffs. We assume that there are two heterogeneous objects and two bidders, and that each bidder does not know the other bidder's material payoff structure. We conducted the laboratory experiments for eight payoff structures associated with complements and substitutes. We compare three types of auction formats, i.e., sequential first price auction, clock auction, and VCG mechanism.

more »

... We also research questionnaires concerning the subjects' impressions about the performance of these formats. The experimental results imply that the VCG mechanisms generally function very well, while the performance of the clock auctions is pretty bad in some cases. These observations are in contrast with the results of the questionnaires.