Competitive market equilibrium under asymmetric information

This paper studies the existence of a competitive market equilibrium under asymmetric information. There are two agents involved in the trading of the risky assets: an “informed” trader and an “ordinary” trader. The market is competitive and the ordinary agent can infer the insider information from the price dynamics of the risky assets. The insider information is considered to be the total supply of the risky assets. The definition of market equilibrium is based on the law of supply-demand as described by a rational expectations equilibrium of the Grossman and Stiglitz (Am Econ Rev 70:393–408, 1980) model. We show that equilibrium can be attained by linear dynamics of an admissible price process of the risky assets for a given linear supply dynamics.      

Self-organized criticality in a herd behavior model of financial markets

This paper explains the fat-tail distribution of asset transaction volumes and prices by a model of rational herd behavior of traders. Each trader decides whether to buy an asset by observing private information and other traders’ actions. A trader’s buying action reveals his positive private information and affects the other traders’ beliefs in favor of buying, leading to strategic complementarity. A power-law distribution emerges for the number of buying actions in a static Nash equilibrium. This model provides an economic reason as to why the stock market has to exhibit a criticality in the connectivity of the traders’ actions. I am benefited by comments from the seminar participants at University of Tokyo and the Econophysics Colloquium 2006 at International Christian University, the editors of the special issue, and particularly an anonymous referee.     

Information asymmetry,sentiment interactions,and asset price

We develop an asset pricing model with sentiment interactions between institutional and individual investors under the condition of information asymmetry. Our model considers private information and investor sentiment, two imperfections in securities markets, and integrates them into a theoretical model to investigate the role of the interaction between information asymmetry and investor sentiment in asset pricing. We show that the joint effect of private information and investor sentiment deviate the price of risky assets and efficiently explains anomalies in the stock market. Investor sentiment changes the effect of information on the equilibrium price relative to a world where all investors are completely rational. Private information changes the effect of investor sentiment on the equilibrium price in comparison with a scenario with symmetric market information. In addition, the individual investors’ learning and the disclosure of information both allow private information to be better integrated into the price and simultaneously changes the effect of investor sentiment on the equilibrium price.     

A link between random coefficient autoregressive models and some agent based models

An agent based model (ABM), where each agent makes decisions by using the sum of two signals, is proposed. The first is related to the fundamental information while the second comes from trader’s idiosyncratic noise. This model entails the switching between two groups called fundamentalist and noise traders. Additionally, if the price impact function is log-linear, then the dynamic of log asset prices belongs to the class of random coefficient autoregressive RCA(p) models, which are known to share important stylized facts of financial prices.     

Optimal speculative trade among large traders

A collection of large traders holds heterogeneous prior beliefs regarding market fundamentals. This gives them a motive to engage in speculative trade with respect to market prices. Rather than assuming a particular institution or market for speculative trade, we take a mechanism-design approach by attempting to characterize the mechanism that maximizes the traders’ gains from speculative trade, subject to the incentive constraints that result from the traders’ ability to manipulate market prices. Within a stylized market model, we show that this mechanism affects price volatility without destroying ex-post efficient allocations. We also characterize the implementability of optimal speculative trade when the traders’ prior beliefs are private information. Financial support from the US-Israel Binational Science Foundation, Grant No. 2002298 is gratefully acknowledged.     

Margin trade,short sales and financial stability

We model how leveraged trading activities constrained by dynamic funding availability affect financial stability. In the market, customers trade based on the fundamental value of the risky asset and make full payment for their transactions, while speculators take trading position based on margin, which is constantly adjusted by the financier, the fund provider, according to the price volatility. As a result of equilibrium price discontinuity triggered by dynamic margin requirements, trivial shocks to external supply, wealth or fundamental value can be transmitted into asset price crashes or jumps. We find that tightening margin requirements improves (mitigates) the market liquidity in the bull (bear) market, and that imposing short sale constraints helps prevent the price from falling further when the asset is sufficiently under-priced and accelerate price collapse when the asset is over-priced.

     

Self-organization and the persistence of noise in financial markets

A dynamic model of financial markets with learning is demonstrated to produce a self-organized system that displays critical behavior. The price contains private information that traders learn to extract and employ to forecast future value. Since the price reflects the beliefs of the traders, the learning process is self-referencing. As the market learns to correctly extract information from the price, the market deemphasizes private information. Despite the convergence of the model towards the parameters producing efficiency, pricing deviations remain constant due to the increased sensitivity of the price to small errors in information extraction produced by the model's own convergence.     

Rational asset pricing bubbles and debt constraints

Rational price bubble arises when the price of an asset exceeds the asset’s fundamental value, that is, the present value of future dividend payments. The important result of Santos and Woodford (1997) says that price bubbles cannot exist in equilibrium in the standard dynamic asset pricing model with rational agents facing borrowing constraints as long as assets are in strictly positive supply and the present value of total future resources is finite. This paper explores the possibility of asset price bubbles under endogenous debt constraints induced by limited enforcement of debt repayment. Equilibria with endogenous debt constraints are prone to have infinite present value of total resources. We show that asset price bubbles are likely to exist in such equilibria. Further, we demonstrate that there always exist equilibria with price bubbles on assets in zero supply.     

Prospect theory and risk appetite: an application to traders’ strategies in the financial market

According to behavioral finance theories, in this article we develop a dynamic model with heterogeneous traders, where the asset price is determined by the interaction among four different groups of agents: trend reversers, trend followers, risk averters and risk seekers. The main purpose of the study is centered on modeling and testing how the market efficiency changes along with the changes of agent’s behavior preference without exogenous influence. Combining with the assumption of risk appetite and prospect theory, focusing on analyzing the rules for selecting strategies, we establish a more reliable and comprehensive dynamic mechanism. In particular, our study suggests that diversified trading strategies will help to realize market efficiency.     

Reputation and Managerial Truth-Telling as Self-Insurance

We investigate truth-telling by an informed insider, or manager, who repeatedly forecasts cash flows to competitive investors in a standard message game. The insider cannot trade on or sell private information, but faces imperfectly hedgeable nonwage income shocks. When compensation depends on the current stock price, a partially revealing equilibrium may exist in which the manager manipulates his reports, and hence the stock price, to reduce consumption variance. Intuitively, the manager builds reputation in good times when honesty is affordable, and exploits reputation in times of need. Endogenous reputation for honesty thus follows from a self-insurance motive.     

Impact of investor’s varying risk aversion on the dynamics of asset price fluctuations

While investors’ responses to price changes and their price forecast have been identified as one of the major factors contributing to large price fluctuations in financial markets, our study shows that investors’ heterogeneous and dynamic risk aversion (DRA) preferences may play a more critical role in understanding the dynamics of asset price fluctuations. We allow an agent specific and time-dependent risk aversion index in a popular power utility function with constant relative risk aversion to construct our DRA model in which we made two key contributions. We developed an approximated closed-form price setting equation, providing a necessary framework for exploring the impact of various agents’ behaviors on the price dynamics. The dynamics of each agent’s risk aversion index is modeled by a bounded random walk with a constant variance, and such dynamics is incorporated in the price formula to form our DRA model. We show numerically that our model reproduces most of the “stylized” facts observed in the real data, suggesting that dynamic risk aversion is an important mechanism for understanding the dynamics of the financial market and the resultant financial time series.     

Portfolio Selection under Maximum Minimum Criterion

In this paper, we studied the problem of risky portfolio selection under uncertainty. Different from risk-return analytical methodology, we formulated a model under maximum minimal criterion of uncertain decision-making theory. If the investor had no any distribution information of the returns and (s)he knew the variation scopes of the returns by his/her knowledge of the market information or experts’ evaluations of the alternative risky assets, then we showed that the optimal portfolio strategy of the model under maximal minimal criterion could be obtained by solving linear programming. If the returns were known to be normal distributed, the investor’s optimal portfolio strategy could be obtained by solving a nonlinear programming. The paper also provided an algorithm to solve this programming. At last, the paper compared this model with Markowitz’s mean-varience (M-V) model and Young’s minmax model, and pointed out the distinctions and similarities between our model and the other two. Supported in part by Program for NCET, in part by the Key Project of Chinese Ministry of Education 104053.     

The joint decision to manage earnings through discretionary accruals and asset sales around insider trading: Taiwan evidence

This study assesses the joint decision of multiple earnings–management tools around insider trading. The Taiwanese evidence indicates significantly higher magnitudes of both discretionary accruals and asset sales before insider selling. In addition, to investigate the endogenous relationship between discretionary accruals and asset sales, this study develops a set of simultaneous equations and includes the inverse Mill’s ratio as a regressor to account for firms that choose not to use asset sales. The results indicate a marginal complementary correlation between discretionary accruals and asset sales before insider selling. Further tests find this complementary correlation becomes stronger when accompanying abnormal insider selling. The findings support the view that insiders consider both tools jointly and adjust them as complements to meet their directional earnings management objective.     

Equilibria,stability and asymptotic dominance in a speculative market with heterogeneous traders

We consider a pure exchange economy where one risky and one riskless security are traded in discrete time. Individual demands are expressed as fractions of individual wealth and depend on traders’ forecasts about future price movement.Introducing the ‘Equilibrium Market Line’ as the locus of all possible equilibrium returns, we show that, irrespectively of the number of traders and of their investment behavior, the economy possesses isolated equilibria where a single agent dominates the market and continuous manifolds of equilibria where many agents hold finite wealth shares. Moreover, we prove that no global dominance order relation among strategies can be defined.     

Asset allocation and multivariate position based trading

I add a second risky asset and a risk free bond to the univariate artificial market investigated by Lux and Marchesi (Int J Theor Appl Finance 3(4):675–702, 2000), keeping track of traders aggregate positions and wealth. Asset allocation and security selection are modeled as separate decision processes, as is common practice in financial institutions. Introducing position based trading avoids inconsistencies in traders inventories resulting from the order based setup of the original model, while preserving its ability to reproduce the stylized facts of financial return series.      

Do Managers Trade on Public or Private Information? Evidence from Fundamental Valuations

Using accounting-based (residual income) valuations, this study examines the extent to which abnormal returns after insider share trades are explained by private information versus mispricing of public information. For a sample of insider trades in the Netherlands (1999–2008), I find that managers' share purchase decisions are associated with positive future abnormal returns as well as equity undervaluation. Even though undervaluation results in predictable price increases, positive abnormal returns following purchases persist after controlling for fundamental valuations. Thus, this study provides evidence on the sources of managers' personal trading gains and suggests that positive abnormal returns after insider share purchases reflect both private information and managers' responses to market mispricing of public information.     

Rational expectations equilibrium and the strategic choice of costly information

This paper studies costly information acquisition in one-good production economies when agents acquire private information and prices transmit information. Before asset markets open, agents choose the quality of their private information. After this information stage, agents trade assets in sequentially complete markets taking into account their private information and the information revealed by equilibrium prices (rational expectations equilibrium, (Radner, R., 1979. Rational expectations equilibrium: generic existence and the information revealed by prices, Econometrica 47, 655–678.)). An overall equilibrium in asset and information market is defined as a Nash equilibrium of the information game in which agents’ actions are information choices and their utility payoffs are the ex-ante expected utilities of the corresponding rationale expectations equilibrium. This paper shows that for a generic set of economies parameterized by endowments and productivity shocks, an overall equilibrium in information and asset market (a Nash equilibrium of the induced information game) with costly information acquisition and fully-revealing prices exists. In other words, informational efficiency is in general consistent with costly information acquisition.     

Two-period model of insider trading with correlated signals

In this article, we extend the one-period model of Jain and Mirman (1999) for asset trading with two correlated signals to a two period model. We then prove the existence and uniqueness of the Bayesian linear equilibrium. Finally, we perform comparative statics analysis with respect to Kyle (1985). Our findings reveal that adding another correlated signal (the real signal) to the total order flow of Kyle (1985), increases the amount of information incorporated in the stock price at each period and decreases the insider’s expected profits at each period.     

Should managers refrain from and investors ignore noisy dividend surprises? Some experimental evidence

A series of experiments is conducted in an asset market that contains a high productivity firm and a low productivity firm. Managers' compensation is a positive function of the market determined value of the firm. Investment decisions are made endogenously and are private information to the managers. The results of the experiments indicate that managers signal earning's information via noisy dividend announcements that result in suboptimal investment decisions. A manager's overinvestment in the signal does not generate significant increases in managerial compensation. The noisy signal does not pay off and in fact would result in a tendency for the market to underpredict earnings. This implies that even in the presence of suboptimal contracts between the managers and the firms, managers are not overcompensated. Thus, in these experiments the signal does not “solve” the dividend puzzle.     

Solving DSGE portfolio choice models with dispersed private information

Noisy rational expectations models, in which agents have dispersed private information and extract information from an endogenous asset price, are widely used in finance. However, these linear partial equilibrium models do not fit well in modern macroeconomics that is based on non-linear dynamic general equilibrium models. We develop a method for solving a DSGE model with portfolio choice and dispersed private information. We combine and extend existing local approximation methods applied to public information DSGE settings with methods for solving noisy rational expectations models in finance with dispersed private information.