Dominance of a Class of Stein type Estimators for Optimal Portfolio Weights When the Covariance Matrix is Unknown

For the estimation problem of mean-variance optimal portfolio weights, several previous studies have proposed applying Stein type estimators. However, few studies have addressed this problem analytically. Since the form of the loss function used in this problem is not of the quadratic type commonly used in statistical studies, there have been some difficulties in showing analytically the general dominance results. However, dominance results are given here of a class of Stein type estimators for the mean-variance optimal portfolio weights when the covariance matrix is unknown and is estimated. The class of estimators is broader than the one given in a previous study. The results we have obtained enable us to clarify conditions for some previously proposed estimators in finance to have smaller risks than the estimator which we obtain by plugging in the sample estimates.     

On the Optimality of Portfolio Insurance

This paper examines the optimality of an insurance strategy in which an investor buys a risky asset and a put on that asset. The put's striking price serves as the insurance level. In complete markets, it is highly unlikely that an investor would utilize such a strategy. However, in some types of less complete markets, an investor may wish to purchase a put on the risky asset. Given only a risky asset, a put, and noncontinuous trading, an investor would purchase a put as a way of introducing a risk-free asset into the portfolio. If, in addition, there is a risk-free asset and the investor's utility function displays constant proportional risk-aversion, then the investor would buy the risk-free asset directly and not buy a put. In sum, only under the most incomplete markets would an investor find an insurance strategy optimal.     

基于雅可比矩阵下一种新的证券组合策略

在当前的金融环境下,不同产业之间交互渗透,各公司相互持股,仅依靠单一证券很难将风险分散出去,本文将目光放于组合证券,运用雅可比矩阵判断其相关性,从中选出相关性为0的组合证券,并对它们进行组合,从而最大程度的降低投资风险。     

On the Demand for Portfolio Insurance

While insurers manage underwriting risk with various methods including reinsurance, insurers increasingly manage asset risk with options, futures, and other derivatives. Previous research shows that buyers of portfolio insurance pay considerably for downside protection. We add to this literature by providing the first evidence on the cost of portfolio insurance, the payoff to portfolio insurance, and the relative demand for portfolio insurance across VIX levels. We find that the demand for portfolio insurance is relatively high at low levels of VIX, suggesting purchasers demand more downside protection when this protection is cheap on an absolute basis (but expensive on a relative basis). We also provide the first evidence on the hedging behavior of specific investor classes and show that the demand for portfolio insurance is driven by retail investors (individuals) who buy costly insurance from institutional investors. Results are consistent with other types of paradoxical insurance‐buying behavior.     

Graphical Portfolio Analysis

This paper presents a new methodology for portfolio analysis based on the correspondence between the expression for the standard deviation of a two-asset portfolio and the magnitude of the sum of two complex numbers. This approach offers a geometric alternative to traditional portfolio analysis. The pedagogical advantages of the new framework are illustrated by rederiving many efficient set mathematics results. A previously unrecognized fact is uncovered using the graphical technique that the sum of the maximum and minimum betas for efficient portfolios is 1, so knowledge of one extreme beta implies knowledge of the other.     

一类广义范得蒙矩阵的求逆递推算法

在给定的若干个线性方程组有解的条件下给出了一类广义范得蒙矩阵的求逆递推公式,推广了文献①的结果.     

Equilibrium Analysis of Portfolio Insurance

A martingale approach is used to characterize general equilibrium in the presence of portfolio insurance. Insurers sell to noninsurers in bad states, and general equilibrium requires that the risk premium rises to induce noninsurers to increase their holdings. We show that portfolio insurance increases price volatility, causes mean reversion in asset returns, raises the Sharpe ratio and volatility in bad states, and causes volatility to be correlated with volume. We also explain why out-of-the-money S&P 500 put options trade at a higher volatility than do in-the-money puts.     

On Viable Diffusion Price Processes of the Market Portfolio

The assumption that the market portfolio follows a specified diffusion process implies, in a simple equilibrium framework, that the representative individual must have a certain utility function which is identified in the paper. Not every diffusion process is viable, i.e., can be “endogenized” to be the market portfolio's price process in such an equilibrium model. The paper provides necessary and sufficient conditions for viability which imply that viable diffusion processes constitute a rather restricted family.     

美国谨慎投资者规则与现代投资组合理论探析

谨慎投资者规则是英美法系指导受托人投资的基本原烈，其衙生于受托人的谨慎义务，先后经历了谨慎人规则、哈佛学院规则和新谨慎投资者规则。现代投资组合理论是美国新谨慎投资者规则的经济学渊源，后者融入了现代投资组合理论的精髓，值得我国在信托投资立法时借鉴。     

An Analysis of Covariance Risk and Pricing Anomalies

This article examines the link between several well-known assetpricing "anomalies" and the covariance structure of returns.I find size, book-to-market, and momentum strategies exhibita strong, weak, and negligible relation to covariance risk,respectively. A size factor helps predict future volatilityand covariation, improving the efficiency of investment strategies.Moreover, its premium rises following increases in both itsvolatility and covariation with other assets. These effectsare amplified in recessions. No such relations exist for book-to-marketor momentum. These findings may shed light on explanations forthese premia and present a challenging set of facts for futuretheory.     

Portfolio Analysis with Factors and Scenarios

Recently there has been a growing interest in the scenario model of covariance as an alternative to the one-factor or many-factor models. We show how the covariance matrix resulting from the scenario model can easily be made diagonal by adding new variables linearly related to the amounts invested; note the meanings of these new variables; note how portfolio variance divides itself into “within scenario” and “between scenario” variances; and extend the results to models in which scenarios and factors both appear where factor distributions and effects may or may not be scenario sensitive.     

再保险业务组合风险的实证分析

为了充分反映再保险业务线之间的相依性结构以及由此而产生的风险分散化效应,本文用完全正相关假设及学生t联接函数的3种形式来评估一个再保险组合的风险价值(VaR)和尾部条件预期(TCE),认为联接函数的选择对多业务线保险公司的资本需求和分散性效应都有明显影响。学生t类联接函数能够灵活反映多业务线之间相依性的联接函数,随着自由度的变化,可以模拟损失分布之间的不同相依性结构。     

Copula的投资组合选择模型的应用研究

结合Copula技术和GARCH模型,建立了投资组合的Copula-GARCH模型。由于该模型可以捕捉金融市场间的非线性相关性,因而可用于投资组合的风险分析中。利用这个模型,并结合Markowitz的投资组合选择模型,对我国的一支开放式基金——中信红利精选股票型证券投资基金投资组合的选择进行了优化,本文应用lingo 8.0,在收益率一定的情况下,得到了风险(VaR)最小的投资组合。     

On the Jensen Measure and Marginal Improvements in Portfolio Performance: A Note

The marginal performance contribution made by new assets in a portfolio is identified. The maximum change in a portfolio's Sharpe performance from the addition of new assets is a simple function of a generalized Jensen index and the unexplained covariances from a multivariate market model. Deviations from a higher dimension market line may be used to rank the desirability of asset additions to an existing portfolio. Statistical tests for the equality of the performance contributions by new assets is possible.     

基于资产组合法的企业价值评估研究

本文引入资产组合概念对企业的价值评估问题进行建模。文章将资产结构的合理性作为评估企业价值的重要依据,通过确定出最佳的资产组合模式来测算企业的价值。在这一研究过程中,本文构建了有效资产组合和非有效资产组合下的企业价值评估模型,并通过具体的算例,验证了这一方法的可行性。     

证券投资基金组合AHP模型分析

利用AHP方法,为证券投资基金选择投资组合提供一种思路,在专家确定的几种投资组合中进行优劣比较,以确定不同基金不同时期的最佳组合.