Bidding strategies for real-life small loan auctions

We define and identify bidding strategies in real-life small loan auctions (Prosper.com). In such auctions, lenders bid for borrowers' loan listings and the winners get to fund the loan at an interest rate determined by the auction. The exceptionally large empirical database provided by Prosper.com offers a unique opportunity to test and further develop the theory of online auctions. This study shows that bidding behavior is not homogeneous among bidders, as the traditional auction theory suggests. Instead, bidders use many different bidding strategies. Moreover, learning and bidders' consistency over time in different auctions is studied.     

Should we collude? Analyzing the benefits of bidder cooperation in online group-buying auctions

Cooperation among bidders in traditional auctions is typically forbidden. This is because it is viewed as being harmful to the interests of sellers, who hope to obtain fair prices for their sale items. It also may be harmful to other bidders who are not able to take advantage of any cooperation that is occurring. In online group-buying auctions, in contrast to traditional auctions, cooperation results in higher welfare, leading to market expansion that benefits buyers and sellers, as well as the auction intermediary. This has not been well understood in prior research, however. In this article, we show how the online group-buying auction mechanism on the Internet can be effectively enhanced to produce higher welfare for the participants. The key to achieving this, we find, is for the auction intermediary to provide a means for bidders to cooperate, so as to collectively express greater demand. Such cooperation, it turns out, permits the group-buying auction mechanism to dominate the fixed-price mechanism from the seller’s point of view under some circumstances. Through an analytical modeling analysis, we offer insights into how sellers can set their group-buying auction price curves more effectively, so as to take advantage of bidder cooperation to improve auction performance. We further argue that the goal of the auction intermediary should be to offer an information sharing mechanism to facilitate bidding ring formation, as a means to maximize the value of this market mechanism.     

Reactivity based model to study online auctions dynamics

Online auctions have challenged many assumptions and results from the traditional economic auction theory. Observed bidder behavior in online auctions often deviates from equilibrium strategies postulated by economic theory. In this research, we consider an online auction as an information system that provides a long-duration, information-rich, dynamic application environment in which users (bidders) interact with the system in a feedback loop, in what we term reactivity. Bidders react to the observed conditions of the auction and events triggered by actions of other bidders. In this work we propose a new characterization model with the purpose of isolating the segments of the auction in which users react to the auction conditions and events. Through this model, it is possible to enrich the auction characterization. Despite the existence of other bidding characterization models, none of them is enough for understanding the factors that characterize and explain the auction dynamics. We present results which demonstrate the advantages of applying our methodology. The final objective is to gain an understanding of what drives the dynamics of online auctions, the role of reactivity in the auction dynamics, and how the outcome of the auction is affected by the particular dynamics of the system.

Reference price effect and its implications for decision making in online auctions: An empirical study

Simultaneous supplies of an item by multiple online auction vendors greatly reduce the burden of arduous search that a consumer has to conduct in a brick-and-mortar market. The enriched information set endows all auction participants with added decision flexibility and complexity. One of such flexibilities or complications is the potential of information cross-referencing. In this study, we empirically tested if and how bidders interacted with each other through cross-referencing. Our results strongly supported the existence of cross-referencing. We also identified new strategies and tactical moves as best responses for sellers and bidders under the online simultaneous condition. This research provided another support for the path-dependent nature of online auctions as bidders were found to actively adjust their behavior in avoidance of winner's curse.     

Design of online auctions: Proxy versus non-proxy settings

Recent years have witnessed the rapid development of online auctions. Currently, some online auctions, such as eBay, introduce a proxy bidding policy, under which bidders submit their maximum bids and delegate to a proxy agent to automatically outbid other competitors for the top bidder, whereas other online auctions do not. This paper compares these two widely used auction mechanisms (proxy setting and non-proxy setting) and characterizes the equilibrium bidding behavior and the seller's expected revenue. We find the proxy auction outperforms the non-proxy auction in terms of the seller's expected revenue. This dominance result is not prone to the specific bid announcement policy, the bidder's knowledge regarding the number of bidders, the impact of traffic congestion along the bidding process, the number of items sold through the auction, and the existence of a reserve price.We further find that the proxy setting usually fails to sustain the truthful bidding as a dominant strategy equilibrium even if no minimum bid increments are adopted, and the possibility of a low-valuation-bidder dilemma where the low-valuation bidders could be better off if all bidders collude to bid at the last minute. We also discuss the dramatically different equilibrium bidding behaviors under the two auction mechanisms.     

Improving the Performance of Online Auctions Through Server-side Activity-based Caching

Online auction sites have very specific workloads and user behavior characteristics. Previous studies on workload characterization conducted by the authors showed that (1) bidding activity on auctions increases considerably after 90% of an auction’s life time has elapsed, (2) a very large percentage of auctions have a relatively low number of bids and bidders and a very small percentage of auctions have a high number of bids and bidders, (3) prices rise very fast after an auction has lasted more than 90% of its life time. Thus, if bidders are not able to successfully bid at the very last moments of an auction because of site overload, the final price may not be as high as it could be and sellers, and consequently the auction site, may lose revenue. In this paper, we propose server-side caching strategies in which cache placement and replacement policies are based on auction-related parameters such as number of bids placed or percent remaining time till closing time. A main-memory auction cache at the application server can be used to reduce accesses to the back-end database server. Trace-based simulations were used to evaluate these caching strategies in terms of cache hit ratio and cache efficiency. The performance characteristics of the best policies were then evaluated through experiments conducted on a benchmark online auction system.     

A theoretical and empirical investigation of multi‐item on‐line auctions

In this paper we explore and analyze the structure of Internet auctions from an analytical and an empirical perspective. Such web‐based auctions are rapidly emerging as a mercantile process of choice in the electronic marketplace. We observe current Internet auctions for one‐time products, such as rapidly aging hardware, and analyze them within the framework of the existing auction theory. While traditional auction theory focuses on single‐item auctions, we observe that a majority of on‐line auctions are multi‐item auctions. A significant contribution of this work is the theoretical derivation of the structure of the winning bids in multi‐item progressive on‐line auctions. Additionally, for comparative purposes, we explore the structural characteristics of alternative multi‐item auction mechanisms proposed in the auction theory. We derive hypotheses based on our analytical results and compare two different types of auction mechanisms. We test the traditional auction theory assumption regarding the homogeneity of bidders and present the first ever empirically derived classification and performance‐comparison of on‐line bidders. We test our hypotheses using real‐world empirical data obtained by tracking a premier web‐based auction site. Statistical analysis of the data indicates that firms may gain by choosing alternative auction mechanisms. We also provide directions for further exploration of this emerging but important dimension of electronic commerce. This revised version was published online in July 2006 with corrections to the Cover Date.     

Strong activity rules for iterative combinatorial auctions

Activity rules have emerged in recent years as an important aspect of practical auction design. The role of an activity rule in an iterative auction is to suppress strategic behavior by bidders and promote simple, continual, meaningful bidding and thus, price discovery. These rules find application in the design of iterative combinatorial auctions for real world scenarios, for example in spectrum auctions, in airline landing slot auctions, and in procurement auctions. We introduce the notion of strong activity rules, which allow simple, consistent bidding strategies while precluding all behaviors that cannot be rationalized in this way. We design such a rule for auctions with budget-constrained bidders, i.e., bidders with valuations for resources that are greater than their ability to pay. Such bidders are of practical importance in many market environments, and hindered from bidding in a simple and consistent way by the commonly used revealed-preference activity rule, which is too strong in such an environment. We consider issues of complexity, and provide two useful forms of information feedback to guide bidders in meeting strong activity rules. As a special case, we derive a strong activity rule for non-budget-constrained bidders. The ultimate choice of activity rule must depend, in part, on beliefs about the types of bidders likely to participate in an auction event because one cannot have a rule that is simultaneously strong for both budget-constrained bidders and quasi-linear bidders.     

What Format for Multi-Unit Multiple-Bid Auctions?

This paper uses computational experiments where bidders learn over nonlinear bidding strategies to compare outcomes for alternative pricing format for multi-unit multiple-bid auctions. Multi-unit multiple-bid auctions, in which bidders are allowed to submit multiple price-quantity bids, are promising mechanisms for the allocation of a range of resources. The main advantage of such auctions is to avoid the lumpy bid problem which arises when bidders can only compete on the basis of one bid. However, there is great uncertainty about the best auction formats when multi-unit auctions are used. The theory can only supply the expected structural properties of equilibrium strategies and the multiplicity of potential equilibria makes comparisons across auction formats difficult. Empirical studies and experiments have improved our knowledge of multi-unit auctions but they remain scarce and most experiments are restricted to two bidders and two units. Moreover, they demonstrate that bidders have limited rationality and learn through experience. This paper constructs an agent-based computational model of bidders to compare the performance of alternative procurement auction formats under circumstances where bidders submit continuous bid supply functions and learn over time to adjust their bids in order to improve their net incomes. The setting is for independent private values. We show that bidding behaviour displays more interesting patterns than is depicted in the theoretical literature and that bidding patterns depend on the interplay between heterogeneity in the bidder population and the degree of rationing in the auction. Results indicate that the three auction formats have similar performance for most levels of competition but that their performances differ when competition is weak. This ranking is dependent on whether the population of bidders is homogenous or heterogeneous.     

Bidding strategies in online single-unit auctions: Their impact and satisfaction

Online bidders use different strategies in their biddings. However, we are unsure of the bidders strategies and their effectiveness in achieving auction goals. Our study was an attempt to identify bidding strategies empirically in online single-unit auctions and evaluate their outcome in terms of cost saving, perceived bidder enjoyment, and bidder satisfaction. A research model was developed and used to examine the relationships. Both objective and subjective data of online single-unit auctions were collected from Taobao.com to validate our postulated hypotheses. We found three main bidding strategies: early, snipe, and agent-supported ratchet bidding based on their behavior patterns. These resulted in different levels of winning outcome and cost saving, but had no significant effect on perceived enjoyment. The hypotheses of the relationship between auction outcomes and bidder satisfaction of their bidding strategies were confirmed.     

Real time prediction of closing price and duration of B2B reverse auctions

Nowadays, online auctions have become the most successful business model in the electronic marketplace. To the best of the authors’ knowledge, no other work has been devoted to the prediction of closing price and duration of Business-to-Business (B2B) English reverse online auctions in which goods or service providers compete with each other to win contracts by lowering offering prices with each bid, which is conducted on a virtual platform hosted on the Internet. This research designs and proposes a new methodology to predict closing prices and duration within the first few bids of the corresponding auctions based on real time bidding information rather than static auction information. In this article, we employ real time information and prediction rules to forecast the behavior of live auctions. This is in contrast to the static prediction approach that takes into consideration only information available at the beginning of an auction such as products, item features, or the seller’s reputation. This simulation is based on discretized auction data derived from a B2B online auction marketplace over a two-year period. Three measurements including accuracy, coverage, and benefit are used to evaluate the methodology. Results show that after observing the first 4 bids, this methodology can predict closing prices and duration with 84.6 and 71.9% accuracy, respectively.     

Bidding behavior in dynamic auction settings: An empirical analysis of eBay

We study the impact of dynamic environment of eBay auctions on bidding behavior. Due to high-speed Internet and practically costless search possibilities, bidding behavior is no longer a function of characteristics of a single auction but depends on auctions running simultaneously, completed auctions, available Buy-It-Now prices as well as various outside options. We study how this dynamic market affects a bidder’s choice of participating in an auction or leaving eBay for an outside alternative. We analyze Texas Instruments (TI-83) Graphing Calculator auctions presented on eBay. We estimate a random-effects probit model to study bidders’ probability of staying in eBay, while controlling for unobservable individual-specific heterogeneity. Our main result shows that Market Tightness – the ratio of bidders to sellers – has a negative and significant effect on bidders’ decision to remain in eBay. Moreover, variables containing information from other eBay auctions significantly affect bidders’ participation decision, thus emphasizing the importance of the dynamic, multi-auction environment in eBay marketplace for potential buyers.     

Winner's curse and parallel sales channels—Online auctions linked within e-tail websites

A sample of 416 online auctions was examined to determine the extent of overpayment (winner's curse) where online auctions and e-tail websites were linked together to form a parallel sales channel. The results indicated that 8.7% of the highest winning online auction bidders exceeded e-tail posted reference prices of identical retail merchandise found at the same website. Significantly, such bids exceeded the reference prices by a mean percentage dollar amount of 14.1% thus suggesting the existence of a winner's curse. The results also indicated that (1) there was a significant negative association between reference price and mean percentage dollar amount overbid; (2) there was a significant negative association between auction lot size and mean percentage dollar amount overbid; and (3) there was no significant association between overtime auctions and mean percentage dollar amount overbid. While manipulation of reference price and auction lot size might minimize winner's curse, erratic or irrational behavior (by online auction and/or e-tail websites) may lead to disinformation.     

Exploring the online bidder’s repurchase intention: a cost and benefit perspective

The success of online auctions is founded on bidders enjoying shopping benefits and on creating bidders’ loyalty. This study investigates the importance of bidders’ repurchase intention along with the corresponding cost and benefit aspects. Therefore, this study integrates transaction cost economics and expectancy confirmation theory to understand the determinants of bidders’ repurchase intention in online auctions. We collected data from a survey questionnaire, and a total of 594 valid questionnaires were analyzed. Partial least squares structural equation modeling was used to assess the relationships of the research model. The findings show that satisfaction has a significant influence on bidders’ repurchase intention, while transaction cost is negatively associated with repurchase intention. Bidders’ satisfaction is determined by confirmation and by the e-service quality of both auctioneers and sellers. Moreover, an auctioneer’s asset specificity and product uncertainty are positively associated with the bidder’s perceived transaction cost. The interaction frequency between bidder and seller is negatively associated with the bidder’s transaction costs. The research results provide a novel approach to understanding bidders’ benefit and cost dimensions in online auction marketplaces. Our findings could guide online auctioneers and sellers in enhancing their offerings.     

The relationship between website quality,trust and price premiums at online auctions

This study measures the value of website quality in terms of its impact on trust, intention to transact and price premiums. Prior research on online auctions has focused on the use of reputation systems for building trust in online auction vendors and subsequently to generate price premiums. This study examines the extent to which trust can be induced by improving the quality of online auction listings. A survey of 701 eBay users is conducted which compares the price premiums of two nearly identical online auction businesses, one that has online auction listings with a perceived high quality and the other that has substantially lower perceived quality. Results of this study indicate that website quality can explain 49% of the variation in the trust for eBay sellers. In fact, it shows that sellers with good website quality are all perceived to be equally trustworthy regardless of their eBay reputation; whereas sellers with poor website quality are not perceived to be trustworthy even if they have a high eBay reputation score. The results also show that the trust resulting from increased website quality increases intention to transact and results in price premiums of 12% (on average) for sellers with higher quality listings. Theories from marketing, economics, and social psychology are used to explain why website quality induces trust in unknown vendors without providing any concrete evidence regarding the vendor’s past history.     

Time dynamics of overlapping e-auction mechanisms: Information transfer, strategic user behavior and auction revenue

This paper investigates the time dynamics of user strategic patterns and resulting welfares in a series of overlapping multiple online auctions. An auction mechanism is a dynamic game where the valuation and strategic space of bidders determine the outcomes. When those mechanisms exist concurrently or in a series in a market environment, multiple sources are visible and accessible, such that there is likely to be a form of interdependency across the auctions. While heterogeneous bidder behavior has been studied in some literature, the focus is mainly on an individual auction level and the underlying dynamics regarding the interdependency across the auctions in the market has not been explained. We use a two-phased approach to address this discrepancy. First, we classify user strategy using k-means clustering. Then, we characterize the transition pattern of heterogeneous clusters using a dynamic systems framework. Long-term behavior of the system is effectively and efficiently predicted using system parameters. The empirically calibrated simulation, which supports the analytical properties, provides managerial insights in designing multiple overlapping online auction market.     

一种淘汰式无拍卖行的电子拍卖

在所有的封闭式电子拍卖中存在的一个共同的缺陷结点(tie)问题，即几个投标者同时投了最高价，由于存在着结点严重地影响了拍卖的效率。基于shamir的(t，n)门限体制提出了一种淘汰式无拍卖行的匿名电子拍卖，采用无拍卖行且每个投标者的标价在投标者之间分享实现标价的匿名性的同时，提出了一种淘汰式拍卖解决结点问题，从而使拍卖的效率得到了提高。     

The influence of equivocality in purchasing tasks on the selection of transaction channels in online auctions

Online auctions are one of the most active business models used in electronic commerce. Previous researchers address issues of online auction behaviour focusing on the factors influencing bidding intentions, but how bidders choose transaction channels to complete the consumption process is not examined before. This study conducts an experiment to manipulate the equivocality of purchasing task. Results show that when purchasing a product with higher task equivocality, bidders tend to choose a communication channel with higher information richness, and select a payment and product delivery channel with lower risk. When purchasing a product with lower task equivocality, bidders tend to select a communication channel with lower information richness, and tolerate higher risk to complete the payment and product delivery process.     

An agent-based English auction protocol using Elliptic Curve Cryptosystem for mobile commerce

Rapid development of the Internet and the extensive use of mobile phones have increased demand for mobile devices in Internet auctions. This trend is acting as an incentive to develop an auction model for mobile-based environment. Recently, Kuo-Hsuan Huang proposed a mobile auction agent model (MoAAM), which allows the bidders to participate in online auctions through a mobile agent. He used modular exponentiation operations in his method. As a result, the processing time for key generation, bidding, and verification were long. Thus, we propose to add the concept of Elliptic Curve Cryptosystem (ECC) onto MoAAM, because ECC has low computation amount and small key size, both of which will aid to increase the speed in generating keys, bidding, and verification. In terms of reduction of computation load on mobile devices and auction-manager server, the proposed method will make online auction system more efficient as well as more convenient to use. This paper mainly uses the English auction protocol as the key auction protocol. The protocol consists of four entities: Registration Manager (RM), Agent House (AH), Auction House (AUH), and Bidders (B). The Registration Manager registers and verifies Bidder identity. The Agent House manages the agents and assigns public transaction keys to Bidders. The Auction House provides a place for auction and maintains all necessary operations for a smooth online auction. Bidders are buyers who are interested in purchasing items at the auction. Our proposed method conforms to the requirements of an online auction protocol in terms of anonymity, traceability, no framing, unforgetability, non-repudiation, fairness, public verifiability, unlinkability among various auction rounds, linkability within a single auction round, efficiency of bidding, one-time registration, and easy revocation.