Fundamentalists Clashing over the Book: A Study of Order-Driven Stock Markets

Agent-based models of market dynamics must strike a compromise between the structural assumptions that represent the trading mechanism and the behavioral assumptions that describe the rules by which traders take their decisions. We present a structurally detailed model of an order- driven stock market and show that a minimal set of behavioral assumptions suffices to generate a leptokurtic distribution of short- term log-returns. This result backs up the conjecture that the emergence of some statistical properties of financial time series is due to the microstructure of stock markets.price dynamics, statistical properties of returns, behavioral and structural assumptions, agent-based simulations

On a preferential attachment and generalized P\'{o}lya's urn model

We study a general preferential attachment and Polya's urn model. At each step a new vertex is introduced, which can be connected to at most one existing vertex. If it is disconnected, it becomes a pioneer vertex. Given that it is not disconnected, it joins an existing pioneer vertex with probability proportional to a function of the degree of that vertex. This function is allowed to be vertex-dependent, and is called the reinforcement function. We prove that there can be at most three phases in this model, depending on the behavior of the reinforcement function. Consider the set whose elements are the vertices with cardinality tending a.s. to infinity. We prove that this set either is empty, or it has exactly one element, or it contains all the pioneer vertices. Moreover, we describe the phase transition in the case where the reinforcement function is the same for all vertices. Our results are general, and in particular we are not assuming monotonicity of the reinforcement function. Finally, consider the regime where exactly one vertex has a degree diverging to infinity. We give a lower bound for the probability that a given vertex ends up being the leading one, that is, its degree diverges to infinity. Our proofs rely on a generalization of the Rubin construction given for edge-reinforced random walks, and on a Brownian motion embedding.Comment: Published in at http://dx.doi.org/10.1214/12-AAP869 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Zero-Intelligence Trading without Resampling

This paper studies the consequences of removing the resampling assumption from the zero-intelligence trading model in Gode and Sunder (1993). We obtain three results. First, individual rationality is no longer sufficient to attain allocative effciency in a continuous double auction; hence, the rules of the market matter. Second, the allocative effciency of the continuous double auction is higher than for other sequential protocols both with or without resampling. Third, compared to zero intelligence, the effect of learning on allocative effciency is sharply positive without resampling and mildly negative with resampling.

Simple Market Protocols for Efficient Risk Sharing

This paper studies the performance of four market protocols with egard to allocative efficiency and other performance criteria such as volume or volatility. We examine batch auctions, continuous double auctions, specialist dealerships, and a hybrid of these last two. All protocols are practically implementable because the messages that traders need to use are simple. We test the protocols by running (computerized) experiments in an environment that controls for tradersÕ behavior and rules out any informational effect. We find that all protocols generically converge to the efficient allocation in finite time. An extended comparison over other performance criteria produces no clear winner, but the presence of a specialist is associated with the best all-round performance.market microstructure, allocative efficiency, comparison of market institutions, performance criteria.

Tilting the Supply Schedule to Enhance Competition in Uniform- Price Auctions

Uniform-price auctions of a divisible good in fixed supply admit underpricing equilibria, where bidders submit high inframarginal bids to prevent competition on prices. The seller can obstruct this behavior by tilting her supply schedule and making the amount of divisible good on offer change endogenously with its (uniform) price. Precommitting to an increasing supply curve is a strategic instrument to reward aggressive bidding and enhance expected revenue. A fixed supply may not be optimal even when accounting for the cost to the seller of issuing a quantity different from her target supply.uniform-price auction, divisible good, strategic role of the seller, endogenous supply, Treasury and IPO auctions.

Which market protocols facilitate fair trading?

We study the performance of four market protocols with regard to their ability to equitably distribute the gains from trade among two groups of participants in an exchange economy. We test the protocols by running (computerized) experiments. Assuming Walrasian tatonemment as benchmark, there is a clear-cut ranking from best to worst: batch auction, nondiscretionary dealership, the hybridization of a dealership and a continuous double auction, and finally the pure continuous double auction.allocative efficiency, allocative fairness, allocative neutrality, comparison of market institutions, market microstructure, performance criteria.

Simple market protocols for efficient risk sharing

This paper studies the performance of four market protocols with regard to allocative efficiency and other performance criteria such as volume or volatility. We examine batch auctions, continuous double auctions, specialist dealerships, and a hybrid of these last two. All protocols are practically implementable because the space of messages for traders is simple. We test the protocols by running (computerized) experiments in an environment that controls for traders’ behavior and rules out any informational effect. We find that all protocols generically converge to the efficient allocation in finite time. An extended comparison over other performance criteria produces no clear winner, but the presence of a specialist is clearly associated with the best all-round performance.market microstructure, allocative efficiency, comparison of market institutions, agent-based simulations.