Dynamic Auctions: A Survey

We survey the recent literature on designing auctions and mechanisms for dynamic settings. Two settings are considered: those with a dynamic population of agents or buyers whose private information remains fixed throughout time; and those with a fixed population of agents or buyers whose private information changes across time. Within each of these settings, we discuss both efficient (welfare-maximizing) and optimal (revenue-maximizing) mechanisms.Dynamic auctions and mechanisms, Random arrivals and departures, Changing private information, Incentive compatibility

Progressive Screening: Long-Term Contracting with a Privately Known Stochastic Process

We examine a model of long-term contracting in which the buyer is privately informed about the stochastic process by which her value for a good evolves. In addition, her realized values are also her private information. We characterize the profit-maximizing long-term contract offered by a monopolist in this setting. This optimal contract consists of a menu of deterministic sequences of static contracts. Within each sequence, higher real- ized values lead to greater quantity provision; however, an increasing proportion of buyer types are excluded over time (eventually leading to inefficient early termination of the re- lationship). Moreover, the menu choices differ by future generosity, with more costly (up- front) plans guaranteeing greater quantity provision in the future. Thus, the seller screens buyers in the initial period, and then progressively screens additional buyers so as to re- duce the information rents paid in future periods.Asymmetric information, Dynamic mechanism design, Long-term contracts, Term life insurance, Sequential screening.

The Effect of Peri-Radial Injection of Papaverine Versus Nitroglycerine on Radial Artery Diameter Prior to Cannulation

Objective:The present study aimed to compare the effect of periradial injection of Papaverine versus Nitroglycerine on radial artery diameter prior to cannulation in cardiac surgery patients. We hoped that periradial injection will facilitate the radial artery cannulation and decrease its spasm. Design:This is a prospective randomized controlled trial that included ninety patients scheduled for elective cardiac surgery. Interventions:Patients were randomly assigned into one of three groups: One group received a peri-radial subcutaneous injection of Papaverine and Lignocaine 2% (30 participants); the second group received a peri-radial subcutaneous injection of Nitroglycerine and Lignocaine 2% (30 participants) and a control group that received a peri-radial subcutaneous injection of Lignocaine 2% (30 participants). Measurements and Main Results:The radial artery diameter was measured by ultrasound before the injection and 20 minutes following injection, and the radial pulse palpability score was measured on a score of 1 (being weak) to 3 (being strongly palpable) before the injection and 20 minutes after.We observed a significant increase in radial artery diameter after injection of Papaverine (p< 0.001) and Nitroglycerine (p< 0.001), compared to baseline values, while there was no significant change in the control group. The changes in the Papaverine group were significantly higher (p= 0.003) than that observed in the Nitroglycerine group.The palpatory score of the radial artery was significantly higher in the Papaverine group than the Nitroglycerine group and both are significantly higher than the control group. Conclusions: Papaverine achieved significant increases in radial artery diameter and palpability score

Auctions with Dynamic Populations: Efficiency and Revenue Maximization

We study a setting where objects and privately-informed buyers arrive stochastically to a market. A seller in this setting faces a sequential allocation problem with a dynamic population. We derive both efficient and revenue-maximizing incentive compatible direct mechanisms. Our main result shows that the sequential ascending auction is a simple indirect mechanism that achieves these desirable objectives. We construct equilibria in memoryless strategies where, in every period, bidders reveal all private information. These equilibria are outcome equivalent to the direct mechanisms. In contrast to static settings, sequential second-price auctions cannot yield these outcomes, as they do not reveal sufficient information

Dynamic Markets with Randomly Arriving Agents

We develop a model of a dynamic market with randomly arriving participants. Both buyers and sellers arrive probabilistically over time. The valuation of each buyer for each object is independently distributed and private information to each buyer. Equilibrium prices are determined by a sequence of second-price auctions. We examine the manner in which equilibrium behavior and payoffs are influenced by both current market conditions and anticipated future dynamics

Sequential Auctions with Randomly Arriving Buyers

We analyze a dynamic market in which buyers compete in a sequence of auctions. New buyers and objects may arrive at random times. Buyers' private values, however, are not persistent. Instead, buyers draw new values in every period; equivalently, objects are heterogeneous but are drawn from the same distribution. We consider the use of the second-price auction for selling these objects. In equilibrium, buyers do not bid their true value. Instead, they shade their bids down by their continuation value, which is the option value of participating in future auctions. We show that this option value depends not only on the number of buyers currently present on the market, but also on anticipated market dynamics. We also generalize our results to the setting in which values correspond to a "buyer's market" or a "seller's market" and market conditions evolve, with persistence, from one to the other