In this paper, the authors report on a computer-based laboratory experiment investigating whether disclosing the buyer's preferences in a multi-attribute reverse English auctions affects buyer's utility, suppliers' profits and efficiency. The results show that full revelation of the buyer's preferences significantly increases allocational efficiency. Suppliers use the additional information in their bidding decisions and make weakly significantly more profits. However, the experimental evidence does not support the hypothesis that the buyer is better off when revealing her preferences. At least, the results indicate that the buyer is not exploited by suppliers.

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Multi-attribute reverse auctions have been proposed as market institutions for "electronic request for quotation" buying processes. The choice of a multi-attribute auction institution for corporate sourcing is a challenge for the auctioneer in terms of utility maximization and allocational efficiency. The authors report on a computer-based laboratory experiment in a sole sourcing scenario of a single, indivisible object and investigate whether a multi-attribute reverse English and a multi-attribute reverse Vickrey auction institution lead to identical outcomes with respect to the buyer's utility, suppliers' profits and allocational efficiency. The results show no significant difference in suppliers' profits. However, the English auction institution leads to both higher allocational efficiency and buyer's utility and is thus recommendable to corporate buyers. The documented breakdown of the outcome equivalence of the two auction institutions is attributed to bidders deviating from the dominant bidding strategy. The deviations are analyzed and explained by learning effects.

of doctoral dissertation accepted by the School of Economics and Business Engineering (http://www.wiwi.uni-karlsruhe.de) Universitt Karlsruhe (TH), Germany (http://www.uni-karlsruhe.de) Date of defense: June 23, 2004 Multiattribute auctions provide a buyer with "the ability to retain flexibility during negotiation, and to express tradeoffs across different outcomes without making an up-front commitment to a particular combination of attributes" (Sunderam & Parkes 2002), since the final characteristics of the item, as well as its price, are determined dynamically through suppliers ' bids (Parkes & Kalagnanam 2002). On the other hand, multiattribute auctions allow suppliers to differentiate in the auction process and to bid on their competitive advantages, e. g. offer a faster delivery if production capacity is available (Wise & Morrison 2000).

Abstract. An e-market system is a concrete implementation of a market institution; it embeds one or more exchange mechanisms. E-market systems are also information systems which are information and communication technologies artifacts. This work puts forward an argument that the study of e-markets must incorporate both the behavioral economics as well as the information systems perspectives. To this end the paper proposes a conceptual framework that integrates the two. This framework is used to formulate a model, which incorporates the essential features of exchange mechanisms, as well as their implementations as is artefacts. The focus of attention is on two classes of mechanisms, namely auctions and negotiations. They both may serve the same purpose and their various types have been embedded in many e-market systems.