Portfolio theory—A planning tool

Portfolio theory is a relatively new development in the area of asset selection and diversification. Nevertheless, many articles, books and dissertations have been written to elaborate on the original concepts to such an extent that portfolio theory is now accepted doctrine in the field of finance.Portfolio theory deals with the rules for the intelligent selection of assets under conditions of risk. In this respect it is similar to planning, part of which consists of examining alternative courses of future action. Most of the research concerning portfolio theory has been directed toward the securities markets. Therefore, some of the terminology is investment oriented. Nevertheless, the concepts developed in portfolio theory can be applied to decisions concerning investments or to decisions that are part of a corporate plan. Think of investing in a security as being analogous to investing in a subsidiary, division, or product line. This article explains the major features of portfolio theory with the hope that corporate decision makers will use portfolio theory as a planning tool.     

基于投资组合和现金流的风险投资退出决策研究

本文借鉴投资组合理论,结合项目组合现金流的特点,构建了风险投资项目组合的决策模型,并设计了模型的动态规划求解方法。该模型在保证现金资源合理配置的前提下,考虑了风险投资组合退出的时机与方式,实现了全局收益的最大化。     

OPTIMAL PORTFOLIO SELECTION WITH UPPER BOUNDS FOR INDIVIDUAL SECURITIES*

In this paper, we consider optimal portfolio selection with no short sales and with upper bounds for individual securities. The solution is reached by directy revising the optimal portfolio without upper bounds. Specifically, our analysis is based on the single-index model, as well as the general multi-index model that provides the return generating process for securities in the arbitrage pricing theory. As demonstrated in a simulation study, the proposed algorithm for optimal portfolio selection usually requires very few iterations. Also, since our approach is developed using intuitive reasoning and simple linear algebra, we are able to provide direct and intuitive justifications for the resulting portfolio choice. Therefore this paper should be of interest to both finance academics and practitioners in portfolio management.     

论投资组合与金融优化 ———对理论研究和实践的分析与反思

经过50多年的发展,投资组合选择的理论研究和实践已经取得了相当丰富的成果.随着全球经济一体化进程的加快和我国金融市场的发展与完善,我国金融机构对投资组合理论的应用实践提出了具体要求.按照投资组合选择理论的发展脉络,简述并分析了现代投资组合选择的各种主要理论、模型与方法以及它们之间的内在关系,并对一些最新进展作了重点介绍.在此基础上,对投资组合选择(或广义意义下的金融优化)的理论研究和在我国的应用实践问题,提出了若干值得关注的发展方向与建议.     

基于波动持续性的最优组合构建与分散化研究

构建恰当资产组合来减少风险, 是投资组合理论研究的重要目标.由于金融时间序列的波动往往会伴随着持续性特征, 该种特性会增大组合未来收益的风险.本文通过构建随机波动模型序列持续性最优投资组合模型, 以降低金融资产波动的持续性特征对组合收益波动的影响;并通过研究其分散化水平, 考察该投资组合构建方法的有效性与稳健性.研究发现:与均值方差的组合模型相比较, 序列持续性组合的风险分散化水平更好.此研究在资产组合选择方面, 具有较为重要的理论价值及实践意义.     

基于风险价值偏好的最优投资决策分析

在传统金融理论中,用收益率与方差所构成的效用函数来指导投资者的最优投资决策,这一点在理论上存在一些的缺陷。本文根据行为金融理论中对风险偏好的描述,用风险价值来定量风险偏好,并用这种偏好来指导最优投资决策。     

论投资组合与金融优化 ———对理论研究和实践的分析与反思

经过50 多年的发展,投资组合选择的理论研究和实践已经取得了相当丰富的成果. 随 着全球经济一体化进程的加快和我国金融市场的发展与完善,我国金融机构对投资组合理论 的应用实践提出了具体要求. 按照投资组合选择理论的发展脉络,简述并分析了现代投资组合 选择的各种主要理论、模型与方法以及它们之间的内在关系,并对一些最新进展作了重点介 绍. 在此基础上,对投资组合选择(或广义意义下的金融优化) 的理论研究和在我国的应用实践 问题,提出了若干值得关注的发展方向与建议.     

A fuzzy set approach for R&D portfolio selection using a real options valuation model

Making R&D portfolio decision is difficult, because long lead times of R&D and market and technology dynamics lead to unavailable and unreliable collected data for portfolio management. The objective of this research is to develop a fuzzy R&D portfolio selection model to hedge against the R&D uncertainty. Fuzzy set theory is applied to model uncertain and flexible project information. Since traditional project valuation methods often underestimate the risky project, a fuzzy compound-options model is used to evaluate the value of each R&D project. The R&D portfolio selection problem is formulated as a fuzzy zero–one integer programming model that can handle both uncertain and flexible parameters to determine the optimal project portfolio. A new transformation method based on qualitative possibility theory is developed to convert the fuzzy portfolio selection model into a crisp mathematical model from the risk-averse perspective. The transformed model can be solved by an optimization technique. An example is used to illustrate the proposed approach. We conclude that the proposed approach can assist decision makers in selecting suitable R&D portfolios, while there is a lack of reliable project information.     

具有模糊收益的项目投资组合优化方法

基于可能性理论,研究了投资项目具有模糊收益的多项目投资组合的决策问题。在假设投资项目各年净现金流为三角模糊数的条件下,运用可能性均值和方差,建立了基于现值指数法的单投资项目模糊收益指标和模糊风险评价指标,同时,在此基础上建立了基于模糊可能性均值与方差的多项目投资组合优化模型,提出了最优项目投资组合的算法。最后,给出实际算例说明了方法的可行性和有效性。     

A portfolio model for foreign exchange exposure management

This paper summarizes the results of our research into applications of decision analysis and portfolio theory to the management of foreign exchange exposure. In contrast with much current practice in foreign exchange management, the portfolio approach takes into explicit consideration the inherent relationships among the currencies in the company's foreign currency portfolio. The hedging model developed in this article traces out an ‘efficient frontier’ or trade-off curve between expected value and variance of the foreign currency portfolio at the end of the planning period. In doing so, the model chooses the optimal amount and method of hedging for each currency in the portfolio.     

基于投资者情绪的投资组合模型研究

本文在假设投资者风险厌恶、且其风险厌恶程度受其情绪影响的条件下,以投资者效用最大化为决策目标,建立基于投资者情绪的投资组合模型从理论上研究投资者情绪对投资组合结构及其收益-风险关系的影响。研究结果表明,当投资者过度乐观时,其将通过银行借贷融资等方式购买超额风险资产;当投资者情绪处于相对理性状态时,其将合理分配无风险资产和风险资产的投资比例;当投资者情绪处于悲观状态时,其将卖空风险资产。当投资者情绪处于过度乐观和相对理性状态时,投资组合预期超额收益与风险正相关;当投资者情绪处于悲观状态时,投资组合预期超额收益与风险负相关。论文研究结果修正了前人的相关研究结论,是对传统投资组合理论的深化和发展。     

基于β系数优化的动态投资组合策略研究

本文提出一种股票动态投资组合策略，首先通过上升和下降贝塔来优选行业，然后在选择的行业中构造股票投资组合。对于股票投资组合，利用均值方差投资组合模型作为内核，通过引入参考时间窗口和持有期限窗口两个外生参数构建动态的均值-方差模型，并实证检验了模型的可行性。然后再经过多项业绩评价指标对比分析得出动态投资组合策略的收益明显优于被动投资策略，这种动态投资组合策略能够获得部分超额收益并且具有更好的可靠性。本研究为投资者提供了一种定量的投资组合管理方法，并从侧面验证了我国股市的非有效性。     

均值-方差模型具有一般不确定性下的最优资产组合选择

引入以记忆系数和无差异系数表征的随机变量测度均值-方差模型的一般不确定性特征,反映投资者的模型信任程度,研究均值-方差模型具有一般不确定性下的最优资产组合选择问题。基于资本市场线理论,构建最优资产组合选择是模型信任程度和基于均值-方差模型的传统资产组合选择的线性函数;基于记忆系数和无差异系数的不同组合,运用基于事例推理的方法求解二次效用投资者的最优模型信任程度,获得均值-方差模型具有一般不确定性下的最优资产组合,并以上证综指1997年1月-2014年8月的月度收益数据形成两个研究样本予以实证比较研究。结果表明,较大风险规避投资者,在较大记忆系数和较小无差异系数下,其模型信任程度调整较快、资产组合调整幅度大,表现出可获得性和代表性行为偏差,通常采取积极资产组合策略;反之,其模型信任程度调整渐进、资产组合调整幅度小,表现出锚定性和保守性行为偏差,通常采取消极资产组合策略;模型一般不确定性对最优资产组合选择的影响强于股票市场记忆性的影响。研究体现了投资者的有限理性,将传统的资产组合选择问题延伸至行为金融学领域。     

含流动性约束及保证金购买的多空投资组合选择模型

本文在基于风险资产的价格服从梯形可能性分布的基础上,引入流动性约束、保证金限制、交易成本和存贷利差等因素,建立了多空投资组合模型。利用非线性规划理论和极大熵方法,给出了求解该模型的一种方法。最后,通过实例验证了主要结果并分析了流动性约束、保证金、交易费和存贷利差等因素对投资组合有效前沿的影响。     

不允许卖空下证券投资组合的区间二次规划问题

本文基于经典的Markowitz均值-方差模型,针对市场上不允许卖空的情况,提出了证券投资组合的区间二次规划模型,通过应用区间数排序方法(区间序关系、区间可能度和区间可接受度),给出了两种证券投资组合的区间非线性优化的数学转化模型,从而将不确定性证券投资组合模型转化为确定性的证券投资组合二次规划模型进行求解,并对由本文给出的三种求解方法与传统方法进行了比较。     

求解不允许卖空证券组合前沿的区间搜索方法

综合分析了不允许卖空时证券组合前沿的构成和性质 ,在此基础上给出了求解不允许卖空时证券组合前沿的区间搜索方法 .应用该方法可以方便迅速地求出带有大型协方差矩阵的非负证券组合前沿及构成前沿的全部抛物的解析式 .对于大型证券组合优化问题的求解以及最优证券组合选择理论和方法的实用化具有重要的理论意义和实用价值     

参数不确定性和效用最大化下的动态投资组合选择

标准投资组合选择理论假设投资者准确地知道与资产收益率相关的各种参数(例如均值和方差),忽视了参数不确定性引致的估计风险给投资决策带来的影响.本文研究引入参数不确定和学习时的连续时间动态投资组合选择问题,使用鞅方法求导出了具有CRRA型效用函数的投资者的最优投资策略的显式表达式.在此基础上,我们结合中国证券市场中的实际数据深入分析了参数不确定性以及投资者初始信念对最优投资策略的影响.     

待遇预定制养老基金资产组合与缴费计划最优决策——基于随机波动率Heston模型及Legendre对偶变换法

待遇预定制养老金制度在中国应用非常广泛,缴费制定和资产配置是此类养老金管理的两大核心问题。由此,面对随机波动的现实市场,文章针对待遇预定制养老基金的资产组合管理问题,应用最优控制理论,选用对数效用函数,建立Heston随机波动率模型;在难以求解随机微分Bellman方程的情况下,应用Legendre变换,将原来问题转化为对偶问题,从而求得原问题的解析解。在理论上,进一步丰富了资产组合问题的随机最优控制模型的构建和随机微分方程的求解理论。在实践上,确定了养老金管理风险资产配置比例和缴费水平,给出了最优决策与总资产、发放待遇、净资产与风险溢价之间的数量关系,从而实现养老基金管理的最优资产配置和最低缴费水平的效用目标。     

金融市场条件高阶矩风险与动态组合投资

针对传统组合投资理论没有考虑高阶矩风险和静态处理问题两大缺陷,提出多元GARCHSK模型用于衡量时变的高阶矩风险,基于效用函数的Taylor展开推导出带有高阶矩风险的动态组合投资策略,并利用遗传算法进行求解。实证研究表明,中国股市不仅存在高阶矩风险,而且风险具有时变特征;为防范高阶矩风险,投资者需要动态地修正他的资产配置权重。     

Application of the Fuzzy Weighted Average in Strategic Portfolio Management*

We propose a systematic approach that incorporates fuzzy set theory in conjunction with portfolio matrices to assist managers in reaching a better understanding of the overall competitiveness of their business portfolios. Integer linear programming is also accommodated in the proposed integrated approach to help select strategic plans by using the results derived from the previous portfolio analysis and other financial data. The proposed integrated approach is designed from a strategy‐oriented perspective for portfolio management at the corporate level. It has the advantage of dealing with the uncertainty problem of decision makers in doing evaluation, providing a technique that presents the diversity of confidence and optimism levels of decision makers. Furthermore, integer linear programming is used because it offers an effective quantitative method for managers to allocate constrained resources optimally among proposed strategies. An illustration from a real‐world situation demonstrates the integrated approach. Although a particular portfolio matrix model has been adopted in our research, the procedure proposed here can be modified to incorporate other portfolio matrices.