Hiding information in open auctions with jump bids∗ David Ettinger y Fabio Michelucciz PSL, Universite Paris Dauphine CERGE-EI March 7, 2013 Abstract We analyze a rationale for hiding information in open auction formats. We focus on the incentives for a bidder to call a price higher than the highest standing one in order to prevent the remaining active bidders from aggregating more accurate information that could be gathered by observing the exact drop out values of the exiting bidders. Necessary conditions for the existence of jump bids with such motivations are provided. Finally, we show that there is no clear-cut effect of jump bids on efficiency and expected revenue and introduce several specific results. JEL Classification Numbers: D44, D82. Keywords: auctions, efficiency, jump bids. ∗We would like to thank Levent C¸elik, Fran¸coiseForges, Philippe Jehiel, Marco Pagnozzi, Margaret Meyer, Jakub Steiner and the participants to the Transatlantic Theory Workshop, PET 2012, Dauphine, Naples, Salerno and Lille seminars for helpful discussions and feedback on earlier drafts of this paper. yPSL, Universite Paris Dauphine, LEDa, CEREMADE. Place du Mar´echal de Lattre de Tassigny 75775 Paris Cedex 16 France,
[email protected] zFabio Michelucci, CERGE-EI, P.O. Box 882 Politickych veznu 7 111 21 Praha 1 Czech Republic. Email:
[email protected]. CERGE-EI, a joint workplace of Charles University and the Economics Institute of the Academy of Sciences of the Czech Republic, Politickych veznu 7, 111 21 Prague, Czech Republic. 1 1 Introduction One of the main characteristics of an open ascending auction format is that it allows partici- pants to aggregate new information on top of the information available ex-ante.