We empirically investigate incumbents’ and entrants’ bids on an original dataset of 192 scoring rule auctions for canteen services in Italy. Our findings show that winning rebates are lower (i.e., prices paid by the public buyer are higher) when the contract is awarded to the incumbent supplier. This result is not explained by the observable characteristics of the auction and the service awarded. We develop a simple theoretical model showing that the result is consistent with a setting in which the buyer exploits specific information on the incumbent supplier’s production cost.
We discuss results of experiments made in the 2000s with two different models of acoustic (sonic) black holes. Both structures provide linear decrease of sound velocity. The first one is a series of rigid discs fixed on a rod and placed inside the tube, diameters of discs gradually increase according to a parabolic law. The second one is a tube where effective density of the medium increases due to mass layers placed inside, the concentration of these layers grows toward the end of the tube. If these structures were “perfect”, the sound velocity would decrease so that the wave would never reach the end of the tube. For imperfect (real) models, small addition of absorbers makes absorption very efficient. What is essential, both structures have exact analytical solutions for the wave propagation equation. We study these theoretical results and juxtapose them with the experiments.