Dynamic Optimization of Long-Term Growth Rate for a Portfolio with Transaction Costs and Logarithmic Utility

We study the optimal investment policy for an investor who has available one bank account and n risky assets modeled by log-normal diffusions. The objective is to maximize the long-run average growth of wealth for a logarithmic utility function in the presence of proportional transaction costs. This problem is formulated as an ergodic singular stochastic control problem and interpreted as the limit of a discounted control problem for vanishing discount factor. The variational inequalities for the discounted control problem and the limiting ergodic problem are established in the viscosity sense. The ergodic variational inequality is solved by using a numerical algorithm based on policy iterations and multigrid methods. A numerical example is displayed for two risky assets.     

谈基金投资者教育

目前我国基金投资者数量快速增加,但由于缺乏必要的投资知识和正确的投资理念,不理性和不经济的投资现象比较突出,给投资者带来许多损失,且危及到基金业的健康发展。因此,建立健全基金投资者教育体系,提高投资者素质,就成为业界普遍关心的问题。本文致力于从基金投资者群体特点对国内基金的盲目投资现象进行分析,并为完善基金投资者教育的主要内容和健全多层次基金投资者教育体系提供了切实可行的对策建议。     

Robust Markowitz mean‐variance portfolio selection under ambiguous covariance matrix

This paper studies a robust continuous‐time Markowitz portfolio selection problem where the model uncertainty affects the covariance matrix of multiple risky assets. This problem is formulated into a min–max mean‐variance problem over a set of nondominated probability measures that is solved by a McKean–Vlasov dynamic programming approach, which allows us to characterize the solution in terms of a Bellman–Isaacs equation in the Wasserstein space of probability measures. We provide explicit solutions for the optimal robust portfolio strategies and illustrate our results in the case of uncertain volatilities and ambiguous correlation between two risky assets. We then derive the robust efficient frontier in closed form, and obtain a lower bound for the Sharpe ratio of any robust efficient portfolio strategy. Finally, we compare the performance of Sharpe ratios for a robust investor and for an investor with a misspecified model.     

Hedging and Portfolio Optimization in Financial Markets with a Large Trader

We introduce a general continuous-time model for an illiquid financial market where the trades of a single large investor can move market prices. The model is specified in terms of parameter-dependent semimartingales, and its mathematical analysis relies on the nonlinear integration theory of such semimartingale families. The Itô–Wentzell formula is used to prove absence of arbitrage for the large investor, and, using approximation results for stochastic integrals, we characterize the set of approximately attainable claims. We furthermore show how to compute superreplication prices and discuss the large investor's utility maximization problem.     

DYNAMIC PORTFOLIO OPTIMIZATION WITH A DEFAULTABLE SECURITY AND REGIME‐SWITCHING

We consider a portfolio optimization problem in a defaultable market with finitely‐many economical regimes, where the investor can dynamically allocate her wealth among a defaultable bond, a stock, and a money market account. The market coefficients are assumed to depend on the market regime in place, which is modeled by a finite state continuous time Markov process. By separating the utility maximization problem into a predefault and postdefault component, we deduce two coupled Hamilton–Jacobi–Bellman equations for the post‐ and predefault optimal value functions, and show a novel verification theorem for their solutions. We obtain explicit constructions of value functions and investment strategies for investors with logarithmic and Constant Relative Risk Aversion utilities, and provide a precise characterization of the directionality of the bond investment strategies in terms of corporate returns, forward rates, and expected recovery at default. We illustrate the dependence of the optimal strategies on time, losses given default, and risk aversion level of the investor through a detailed economic and numerical analysis.     

OPTIMAL CONSUMPTION AND PORTFOLIO SELECTION WITH INCOMPLETE MARKETS AND UPPER AND LOWER BOUND CONSTRAINTS

We study an optimal consumption and portfolio selection problem for an investor by a martingale approach. We assume that time is a discrete and finite horizon, the sample space is finite and the number of securities is smaller than that of the possible securities price vector transitions. the investor is prohibited from investing stocks more (less, respectively) than given upper (lower) bounds at any time, and he maximizes an expected time additive utility function for the consumption process. First we give a set of budget feasibility conditions so that a consumption process is attainable by an admissible portfolio process. Also we state the existence of the unique primal optimal solutions. Next we formulate a dual control problem and establish the duality between primal and dual control problems. Also we show the existence of dual optimal solutions. Finally we consider the computational aspect of dual approach through a simple numerical example.     

基于网络平台的湖北上市公司投资者关系管理研究

近年来,国内公司网站在投资者关系管理（IRM）中的应用越来越普及。本文选取湖北证监局于2009年1月公布的有网站的61家湖北上市公司,并以2009年末为观察时间点,考察这些公司基于网站的IRM建设情况发现,湖北上市公司存在网上IRM工作质量参差不齐、总体通过专栏开通率不高、专栏条目设置水平低、内容陈旧、缺乏交互性及参与性、使用界面不完善等问题。其中,监管不够、股东文化意识淡薄及投入不足是湖北上市公司网络IRM水平不高的关键原因,应从加强监管、提高上市公司的重视程度及加大投入等方面做出努力。     

辽宁上市公司融资能力与价值提升

随着资本市场的发展,辽宁上市公司在数量及融资规模上却呈现弱势。这是由于辽宁上市公司资产管理效率低,持续盈利能力和成长性不足;公司治理水平与效率低,缺乏价值创造的内生动力;投资者关系管理表面化,保护投资者利益的积极性和主动性不够。要提高辽宁上市公司融资能力和公司价值,就应改善公司持续盈利能力,提高资产管理效率;完善公司治理结构,提高公司治理水平和效率;加强投资者关系管理,注重投资者利益保护。     

A Puzzle in SRI: The Investor and the Judge

As Socially Responsible Investment (SRI) enters the mainstream of professional and institutional investment practice, some perplexities arise. Some SRI market participants are well schooled in finance but are hesitative as to how to apply non-financial criteria in the management of portfolios. Governments too are giving SRI more attention and, in some countries, are discussion whether and how to regulate the SRI market. Advocacy groups are targeting SRI projects through media campaigns using political discourse. Many of the pertinent questions that come with these perplexities are of the philosophical or ethical type and concern legitimisation, demarcation of responsibilities, interpretation of norms and policy formulation. The inclusion of non-financial criteria into investment decision-making leads to a ‹puzzle in SRI’ for which this article offers a solution. The puzzle arises when the day-to-day implementation of an SRI-policy coincides with the process of administering justice. Three questions make up that puzzle: (1) what should an␣investor do when allegations arise about a corporation, (2) what should an investor do when a corporation is brought before a court, (3) what should an investor do when a corporation is found guilty by a court. This article argues, by distinguishing between the rationality of the investor and that of the judge, that allegations, court cases or court verdicts should not be reasons to disinvest from a corporation. This article offers examples from investor practice and points out in which way allegations, court cases and court verdicts make sense for investor behaviour.     

PORTFOLIO MANAGEMENT WITH CONSTRAINTS

The traditional portfolio selection problem concerns an agent whose objective is to maximize the expected utility of terminal wealth over some horizon. This basic problem can be modified by adding constraints. In this paper we investigate the portfolio selection problem for an investor who desires to outperform some benchmark index with a certain confidence level. The benchmark is chosen to reflect some particular investment objective and it can be either deterministic or stochastic. The optimal strategy for this class of problems can lead to nonconvex constraints raising issues of existence and uniqueness. We solve this optimal portfolio selection problem and investigate the procedure for both deterministic and stochastic benchmarks.     

OPTIMAL LIQUIDATION IN A LIMIT ORDER BOOK FOR A RISK‐AVERSE INVESTOR

In a limit order book model with exponential resilience, general shape function, and an unaffected stock price following the Bachelier model, we consider the problem of optimal liquidation for an investor with constant absolute risk aversion. We show that the problem can be reduced to a two‐dimensional deterministic problem which involves no buy orders. We derive an explicit expression for the value function and the optimal liquidation strategy. The analysis is complicated by the fact that the intervention boundary, which determines the optimal liquidation strategy, is discontinuous if there are levels in the limit order book with relatively little market depth. Despite this complication, the equation for the intervention boundary is fairly simple. We show that the optimal liquidation strategy possesses the natural properties one would expect, and provide an explicit example for the case where the limit order book has a constant shape function.     

交叉上市对公司治理的影响研究——来自我国上市公司的经验证据

以我国A股上市公司2007～2009年的公司为样本,以控股股东占用上市公司资金作为投资者保护水平的变量,对交叉上市、公司治理机构与投资者保护之间的关系的实证分析表明,交叉上市能够减少控股股东占用上市公司资金,提高投资者保护水平。投资者保护水平与控股股东较高的持股比例正相关,但与其他股东的持股比例负相关。国有性质的公司与控股股东占用资金正相关,不利于投资者保护。     

A Generalized Cameron–Martin Formula with Applications to Partially Observed Dynamic Portfolio Optimization

The optimal dynamic allocation problem for a Bayesian investor is addressed when the stock's drift—modeled as a linear mean-reverting diffusion—is not observed directly but only via the measurement process. Adopting a martingale approach, an appropriate generalization of the Cameron–Martin (1945) formula then enables computation of both the optimal dynamic allocation and the value function for a general utility function, in terms of an inverse Laplace transform of an explicit expression. Moreover, closed-form formulas are provided in the case of power utility.     

Institutional investor heterogeneity and firm valuation: Evidence from Latin America

This article analyses how the corporate valuation of Latin American firms is affected by the presence of a blockholder institutional investor. The study uses a data set of 562 firms from six Latin American countries for the 1997–2011 period. We found that the presence of an institutional investor has a positive effect of 8% on firm value, which increases to 21% for the cases where there is blockholder coalition with an institutional investor. After dividing the sample by investor type, we found that independent institutional ownership implies a positive premium on firms' Tobin's Q, while the presence of a grey investor has a negative effect on firm valuation.     

OPTIMAL PORTFOLIO MANAGEMENT WITH FIXED TRANSACTION COSTS

We study optimal portfolio management policies for an investor who must pay a transaction cost equal to a fixed Traction of his portfolio value each time he trades. We focus on the infinite horizon objective function of maximizing the asymptotic growth rate, so me optimal policies we derive approximate those of an investor with logarithmic utility at a distant horizon. When investment opportunities are modeled as m correlated geometric Brownian motion stocks and a riskless bond, we show that the optimal policy reduces to solving a single stopping time problem. When there is a single risky stock, we give a system of equations whose solution determines the optima! rule. We use numerical methods to solve for the optima! policy when there are two risky stocks. We study several specific examples and observe the general qualitative result that, even with very low transaction cost levels, the optimal policy entails very infrequent trading.     

集体诉讼制度与智猪博弈

结合博弈论的有关知识和股市的运行机制 ,有必要引进集体诉讼制度 ,让律师和中小投资者形成智猪博弈中的大猪和小猪 ,促使律师在中小投资者的利益受到侵害后能代表中小投资者从法律途径去制约控股股东 ,从而促使股市正常运转     

ROBUST UTILITY MAXIMIZATION WITH LÉVY PROCESSES

We study a robust portfolio optimization problem under model uncertainty for an investor with logarithmic or power utility. The uncertainty is specified by a set of possible Lévy triplets, that is, possible instantaneous drift, volatility, and jump characteristics of the price process. We show that an optimal investment strategy exists and compute it in semi‐closed form. Moreover, we provide a saddle point analysis describing a worst‐case model.     

The Impact of Internet Commerce on Do-It-Yourself Investing in the IT Sector

ABSTRACT

Recent advances in networking, telecommunications, and the Internet have greatly decreased the problem of information asymmetry for the small investor. Previously, brokerage firms maintained tight control over information thus “encouraging” the investor to partake of their services. The removal of this structural impediment has empowered small investors to take greater control of their personal financial affairs. For those interested in self-directed investing in the growing IT sector, Direct Stock Purchase programs (DSPs), Dividend Reinvestment programs (DRIPs), American Depository Receipts (ADRs), and IT Sector Mutual Funds offer many attractive benefits to shareholders and corporations alike. These investment programs of IT-related firms are examined here.     

VALUATION OF CLAIMS ON NONTRADED ASSETS USING UTILITY MAXIMIZATION

A topical problem is how to price and hedge claims on nontraded assets. A natural approach is to use for hedging purposes another similar asset or index which is traded. To model this situation, we introduce a second nontraded log Brownian asset into the well-known Merton investment model with power law and exponential utilities. The investor has an option on units of the nontraded asset and the question is how to price and hedge this random payoff. The presence of the second Brownian motion means that we are in the situation of incomplete markets. Employing utility maximization and duality methods we obtain a series approximation to the optimal hedge and reservation price using the power utility. The problem is simpler for the exponential utility, and in this case we derive an explicit representation for the price. Price and hedging strategy are computed for some example options and the results for the utilities are compared.     

我国证券市场中小投资者权益的法律保障

中小投资者权益受侵犯是我国证券市场一个突出问题,法律规制是中小投资者权益保护的有效途径。新兴市场法律规制的有效执行需要加强政府监管。我国证券市场要真正保护好中小投资者的权益,必须在法律规制与政府监管方面,进行有效保护投资者权利的核心制度安排,基于投资者本位进行制度设计,完善投资者保护的法律框架,构建强有力的监管架构,建立完善的证券监督体系。