The Actual Structure of eBay’s Feedback Mechanism and Early Evidence on the Effects of Recent Changes

eBay’s feedback mechanism is considered crucial to establishing and maintaining trust on the world’s largest trading platform. The effects of a user’s reputation on the probability of sale and on prices are at the center of a large number of studies. More recent theoretical work considers aspects of the mechanism itself. Yet, there is confusion amongst users about its exact institutional details, which also changed substantially in the last few months. An understanding of these details, and how the mechanism is perceived by users, is crucial for any assessment of the system. We provide a thorough description of the institutional setup of eBay’s feedback mechanism, including recent changes to it. Most importantly, buyers now have the possibility to leave additional, anonymous ratings on sellers on four different criteria. We discuss the implications of these changes and provide first descriptive evidence on their impact on rating behavior

Last Minute Feedback

Feedback mechanisms that allow partners to rate each other after a transaction are considered crucial for the success of anonymous internet trading platforms. We document an asymmetry in the feedback behavior on eBay, propose an explanation based on the micro structure of the feedback mechanism and the time when feedbacks are given, and support this explanation by findings from a large data set. Our analysis implies that the informational content of feedback records is likely to be low. The reason for this is that agents appear to leave feedbacks strategically. Negative feedbacks are given late, in the "last minute," or not given at all, most likely because of the fear of retaliative negative feedback. Conversely, positive feedbacks are given early in order to encourage reciprocation. Towards refining our insights into the observed pattern, we look separately at buyers and sellers, and relate the magnitude of the effects to the trading partners' experience

The Actual Structure of eBay’s Feedback Mechanism and Early Evidence on the Effects of Recent Changes

eBay’s feedback mechanism is considered crucial to establishing and maintaining trust on the world’s largest trading platform. The effects of a user’s reputation on the probability of sale and on prices are at the center of a large number of studies. More recent theoretical work considers aspects of the mechanism itself. Yet, there is confusion amongst users about its exact institutional details, which also changed substantially in the last few months. An understanding of these details, and how the mechanism is perceived by users, is crucial for any assessment of the system. We provide a thorough description of the institutional setup of eBay’s feedback mechanism, including recent changes to it. Most importantly, buyers now have the possibility to leave additional, anonymous ratings on sellers on four different criteria. We discuss the implications of these changes and provide first descriptive evidence on their impact on rating behavior.eBay; reputation mechanism; strategic feedback behavior; informational content; reciprocity; fear of retaliation

Last Minute Feedback

Feedback mechanisms that allow partners to rate each other after a transaction are considered crucial for the success of anonymous internet trading platforms. We document an asymmetry in the feedback behavior on eBay, propose an explanation based on the micro structure of the feedback mechanism and the time when feedbacks are given, and support this explanation by findings from a large data set. Our analysis implies that the informational content of feedback records is likely to be low. The reason for this is that agents appear to leave feedbacks strategically. Negative feedbacks are given late, in the "last minute," or not given at all, most likely because of the fear of retaliative negative feedback. Conversely, positive feedbacks are given early in order to encourage reciprocation. Towards refining our insights into the observed pattern, we look separately at buyers and sellers, and relate the magnitude of the effects to the trading partners' experience.eBay; reputation mechanism; strategic feedback behavior; informational content; reciprocity; fear of retaliation

Market Transparency, Adverse Selection, and Moral Hazard

We study the effects of improvements in market transparency on eBay on seller exit and continuing sellers’ behavior. An improvement in market transparency by reducing strategic bias in buyer ratings led to a significant increase in buyer valuation especially of sellers rated poorly prior to the change, but not to an increase in seller exit. When sellers had the choice between exiting—a reduction in adverse selection—and improved behavior—a reduction in moral hazard—, they preferred the latter because of lower cost. Increasing market transparency improves on market outcomes

Untersuchung einer neuen Herzklappe für Herzunterstützungssysteme

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Ein bewährtes Verfahren zur Behandlung erkrankter natürlicher Heizklappen ist die Implantation von Heizklappenprothesen. Neben diesem Einsatz entwickelt sich zur Zeit ein weiteres Anwendungsgebiet; der Einsatz von Herzklappenprothesen in Herzunterstützungssystemen. Eine häufig dabei auftretende Komplikation stellt die Thrombenbildung dar. Diese tritt insbesondere im Bereich der verwendeten Herzklappenprothesen auf. Bei einer Implantation einer Heizklappenprothese ist ihre unmittelbare Umgebung durch die Anatomie vorgegeben. Bei einem Einsatz in einem Herzunterstützungssystem dagegen kann diese Umgebung frei gestaltet werden. Mit diesem Ansatz ergeben sich für die strömungstechnische Gestaltung der Herzklappen für Blutpumpen ganz neue Möglichkeiten. Die unmittelbare Umgebung der Klappe ist der Strömungskanal. Mit dem neuen, hier vorgestellten S-förmigen Strömungskanal der Klappe scheint es möglich zu sein, die Gefahr der Thrombenbildung zu reduzieren. Insbesondere die Vermeidung von Ablösungen führt zu einer Verringerung des Risikos der Thrombenbildung und ermöglicht damit eine verminderte Dosierung von Antikoagulantien

Adverse selection and moral hazard in anonymous markets

We study the effects of improvements in eBay’s rating mechanism on seller exit and continuing sellers’ behavior. Following a large sample of sellers over time, we exploit the fact that the rating mechanism was changed to reduce strategic bias in buyer rating. That improvement did not lead to increased exit of poorly rated sellers. Yet, buyer valuation of the staying sellers—especially the poorly rated ones—improved significantly. By our preferred interpretation, the latter effect results from increased seller effort; also, when sellers have the choice between exiting (a reduction in adverse selection) and improved behavior (a reduction in moral hazard), then they prefer the latter because of lower cost

Processing acoustic change and novelty in newborn infants

Research on event-related potential (ERP) correlates of auditory deviance-detection in newborns provided inconsistent results; temporal and topographic ERP characteristics differed widely across studies and individual infants. Robust and reliable ERP responses were, however, obtained to sounds (termed ‘novel’ sounds), which cover a wide range of frequencies and widely differ from the context provided by a repeating sound [Kushnerenko et al., (2002) NeuroReport, 13, 1843–1848]. The question we investigated here is whether this effect can be attributed to novelty per se or to acoustic characteristics of the ‘novel’ sounds, such as their wide frequency spectrum and high signal energy compared with the repeated tones. We also asked how sensitivity to these stimulus aspects changes with development. Twelve newborns and 11 adults were tested in four different oddball conditions, each including a ‘standard’ sound presented with the probability of 0.8 and two types of infrequent ‘deviant’ sounds (0.1 probability, each). Deviants were (i) ‘novel’ sounds (diverse environmental noises); (ii) white-noise segments, or harmonic tones of (iii) a higher pitch, or (iv) higher intensity. In newborns, white-noise deviants elicited the largest response in all latency ranges, whereas in adults, this phenomenon was not found. Thus, newborns appear to be especially sensitive to sounds having a wide frequency spectrum. On the other hand, the pattern of results found for the late discriminative ERP response indicates that newborns may also be able to detect novelty in acoustic stimulation, although with a longer latency than adults, as shown by the ERP response. Results are discussed in terms of developmental refinement of the initially broadly tuned neonate auditory system