CAPM在深圳股市的实证检验

作为现代金融投资组合理论体系中得到最广泛应用的核心内容,资本资产定价模型一直是实证检验和学术界瞩目的焦点,也有一些批评家认为它在实际应用中缺乏效力.在目前中国股市存在严重投机行为和缺乏市场效率的情况下,我们在实证检验部分进行了深圳股市的CAPM实证检验.得出研究结论认为深圳股票市场风险和收益关系并不与CAPM理论描述相一致,存在其他因素影响股票市场运行.     

可转换债券市场异常现象的理论研究——基于委托代理问题的资产定价模型

本文旨在研究可转债市场中理论定价和市场定价的偏离问题,通过将公司代理成本融入规范的资产定价模型,得到基于代理的可转债定价模型,证明结合代理成本的可转债定价模型能够很好地解释可转债市场价格和所谓的"理论价格"之间的偏差现象.本文还运用数值分析方法检验分析理论模型的预测结果,得到可转换债券的"微笑现象",与实证研究结果相吻合.     

家庭对不确定性的主观预期与家庭资产配置——基于CHFS微观数据的Tobit实证分析

基于微观层面研究了家庭主观预期对家庭房产、风险资产和无风险资产配置比例的影响机制，并导出三者间的直接联动关系.应用中国家庭金融调查(CHFS)数据和联立Tobit模型估计分析发现，家庭预期利率上升会同时增加无风险资产和风险资产的配置，但减少房产配置；预期风险资产收益下降会减少风险资产配置；预期房价上升会增加房产投资但减少风险资产配置.风险偏好型家庭会加大风险资产配置，且减少房产配置；而风险规避型家庭相反.3类资产配置比例之间存在直接的“挤出效应”,且表现出明显的非对称性：房产和无风险资产对风险资产的“挤出效应”强于各自反向的“挤出效应”,而无风险资产对房产的“挤出效应”在经济意义上强于反向的“挤出效应”.主观预期与风险偏好变量会通过资产配置间的直接影响渠道进一步影响家庭各类资产的配置比例.本研究揭示了中国家庭追求更安全的无风险资产和更高收益的房产投资，且弱化风险资产配置的普遍投资模式，这对政府预期管理与宏观调控、财富管理多投资渠道推荐和家庭合理主观预期形成等具有实际意义.     

收入风险与家庭风险金融资产投资——基于CHFS数据的经验证据

本研究构建了包含金融市场摩擦和背景风险因素的家庭资产配置模型，深入探究了收入风险与家庭风险金融资产投资行为的关系，发现收入风险的增加将显著降低家庭风险金融资产投资，并且市场摩擦和其他背景风险的上升均将加剧收入风险对家庭风险金融资产投资的负效应.同时，本研究使用中国家庭金融调查数据(CHFS)对理论模型的结果进行实证检验，以分组收入方差衡量家庭收入风险，研究结果表明家庭收入风险对风险金融资产投资具有显著负向影响；而信贷约束、社会互动与金融素养等金融市场摩擦因素均显著增强了收入风险对风险金融资产投资的负向效应；在健康、住房及工商业经营和负债等其他背景风险越高的家庭，收入风险对风险金融资产投资的负向影响更显著.     

高风险低收益？基于机器学习的动态CAPM模型解释

我国股票市场存在高风险股票反而伴随较低收益的低风险定价异象,这有悖于传统资产定价理论．本文使用宏观经济和微观企业特征构建了六百多个变量的宏微观混合大数据集,并结合多种经典机器学习算法开发了基于大数据和机器学习的智能动态ＣＡＰＭ模型,检验了时变系统性风险对我国股市收益解释能力．实证结果表明：本文的智能动态ＣＡＰＭ定价模型能够显著解释我国股市低风险定价异象;随机森林等非线性机器学习算法表现最佳;影响股票时变系统风险的主要因素是市场类因子,基本面因子居次．本文对于我国股市系统性风险测度、动态资产定价模型构建和金融与大数据和人工智能融合创新有重要理论与实践指导意义．     

知情交易概率与风险定价——基于不同PIN测度方法的比较研究

分别采用EKOP模型、VPIN模型和VWPIN模型测度了中国证券市场个股的知情交易概率,并实证检验了知情交易概率因子在资产定价中的作用.研究结果表明,基于物理时间和交易量加权的VWPIN模型结合了经典EKOP模型和VPIN模型的优点,可以更简单地估计个股日内任意时间窗口下的信息不对称程度.进一步,关于资产定价的检验结果表明,在控制相关影响因素之后,采用VWPIN模型估计得到的知情交易概率因子与个股收益率之间呈现显著的正相关性,符合理论预期.     

公司债务期限结构与违约风险

在资产风险水平、负债比率等因素一定的情况下,短期债务比例与违约概率呈类U形关系,基于风险规避角度的最优债务期限结构是存在的,并且这一最优短期债务比例与资产风险水平正相关,与负债比率负相关.我国上市公司短期债务比例普遍较高,根据理论预测和实证检验得出,进一步提高短期债务比例将会使公司违约风险继续扩大,进而危及我国的信用体系和金融秩序.     

异质价格预期、无风险利率调整与证券市场波动

基于交易者的异质价格预期规则,构建了二维离散非线性资产价格动态模型,探讨了无风险利率调整对均衡点稳定性的影响,实证检验了2004-2009年期间我国证券市场的波动性.理论分析表明,提高无风险利率易导致证券市场难以形成局部稳定,降低无风险利率则不会从本质上改变稳定性.实证结果显示:相对基准期而言,2006年8月—2008...     

企业负债的违约风险测度

信用风险对于银行、债券发行者和投资者来说是一种非常重要的决策影响因素.本文根据企业资产中债权和股权之间的相互关系,认为股权价值是基于公司资产价格的期权费用,根据戈萨诺夫定理,利用风险资产贴现价格是在特定的概率测度下的鞅,得到了衡量企业负债违约风险的计算公式.     

基于资产链的异质投资者资本资产定价模型

本文基于资产链理论给出投资者的异质预期假设,通过对资产链各节点系统风险的分解,将传统的资本市场线转变为资本市场超平面,建立基于资产链的资本资产定价模型。本文使用小波滤波分解资产收益,对模型在上海A股市场的适用性进行检验,结果表明模型能够区分各类系统风险对资产收益的影响,对资产的平均收益具有显著的解释能力。     

Health insurance system and resilience to epidemics

We theoretically analyze the resilience (efficiency) of health insurance systems and diverse factors including trace and test technology, infection and contagion rates, and social distancing/lockdown policy, in coping with contagious diseases like COVID-19. Our findings can be summarized as follows. First, public insurance is more resilient than market insurance, as the former's investment in test technology is made at the social optimum, whereas the latter's investment is less. The decentralized behavior of competing insurers leads to a less resilient outcome. Second, resilience decreases as the market becomes more competitive because the externality effect becomes more severe. Third, a higher contagion rate, a more cost-efficient test technology or a higher initial infection rate unless it is not too high, leads to a higher test accuracy level. Fourth, the socially optimal social distancing/lockdown policy is determined by comparison between its relative costs and the benefit from contagion reduction.     

THE EFFECTS OF VARIABLE AND FIXED TRANSACTION COSTS ON OPTIMAL INVESTMENT DECISIONS

This paper studies the impact of variable and fixed transaction costs on investment decisions under conditions of risk. The decision model is first formulated as a mixed-integer nonlinear program. The following subjects are then examined: the structure of the investment frontier facing the investor and the effects of transaction costs on this frontier, the impact of transaction costs on the investor's optimal investment strategy, and the conditions for the equilibrium structure of risky asset prices and risk-return relationships. The main finding is that the relaxation of the assumption of the absence of transaction costs eliminates some of the most unattractive implications of the classic capital asset pricing model (CAPM) while preserving the more attractive implications of this model. Also, our model provides explanations for some discrepancies between the theoretical CAPM and empirical findings and, therefore, is a step toward narrowing the gap between theory and practice.     

基于CRRA效用准则的资产负债管理

本文在连续时间不完备市场框架下,考虑了投资者终端时刻资产负债比率的期望效用最大化问题。假设金融市场由1个无风险资产与多个风险资产构成,其中风险资产的价格过程由几何布朗运动刻画;投资者在整个投资时间水平内面临一个由几何布朗运动刻画的外生负债。利用随机动态规划方法,给出了相应的HJB方程与验证定理,并得到了最优投资策略与最优值函数的解析表达式。进一步,通过敏感性分析与数值算例发现：（1）外生负债的预期增长率与当前时刻的资产负债比率对最优投资策略没有影响;（2）在不考虑外生负债时,在最优策略下,投资到风险资产上的资金比例随着风险资产波动率或相对风险厌恶系数的增大而减小,而在考虑外生负债时,并非如此,只有满足一定条件时最优投资策略才是风险资产波动率或相对风险厌恶系数的减函数;（3）不考虑外生负债时,最优值函数是投资时间水平与风险资产预期收益率的增函数,风险资产波动率的减函数,但在考虑外生负债时该结论只在各参数满足一定关系时才成立,否则结论相反。     

分形布朗运动下最优投保和消费策略

基于Merton的最优消费和投资组合模型,通过假设风险资产的价格变化服从几何分形布朗运动,探讨了一类具有人寿保险的最优投资消费问题.首先根据投资者在整个生命周期的消费和投保效用期望值最大的原则,利用贝尔曼动态规划原理,建立了最优投保和消费策略模型.然后在给定消费和遗赠评价效用函数的情况下,给出了最优投保和消费的闭式解,并获得了最优投资组合受模型参数变化影响的一些重要性质.最后,通过数值例子讨论了时间间隔、赫斯特指数变化时最优投保和最大期望效用的变化趋势.     

Optimal market timing strategies under transaction costs

In this paper, we consider optimal market timing strategies under transaction costs. We assume that the asset's return follows an auto-regressive model and use long-term investment growth as the objective of a market timing strategy which entails the shifting of funds between a risky asset and a riskless asset. We give the optimal trading strategy for a finite investment horizon, and analyze its limiting behavior. For a finite horizon, the optimal decision in each step depends on two threshold values. If the return today is between the two values, nothing needs to be done, otherwise funds will be shifted from one asset to another, depending on which threshold value is being exceeded. When investment horizon tends to infinity, the optimal strategy converges to a stationary policy, which is shown to be closely related to a well-known technical trading rule, called Momentum Index trading rule. An integral equation of the two threshold values is given. Numerical results for the limiting stationary strategy are presented. The results confirm the obvious guess that the no-transaction region increases as the transaction cost increase. Finally, the limiting stationary strategy is applied to data in the Hang Seng Index Futures market in Hong Kong. The out-of-sample performance of the limiting stationary strategy is found to be better than the simple strategy used in literature, which is based on an 1-step ahead forecast of return.     

Understanding Mechanisms Underlying Peer Effects: Evidence From a Field Experiment on Financial Decisions

Using a high‐stakes field experiment conducted with a financial brokerage, we implement a novel design to separately identify two channels of social influence in financial decisions, both widely studied theoretically. When someone purchases an asset, his peers may also want to purchase it, both because they learn from his choice (“social learning”) and because his possession of the asset directly affects others' utility of owning the same asset (“social utility”). We randomize whether one member of a peer pair who chose to purchase an asset has that choice implemented, thus randomizing his ability to possess the asset. Then, we randomize whether the second member of the pair: (i) receives no information about the first member, or (ii) is informed of the first member's desire to purchase the asset and the result of the randomization that determined possession. This allows us to estimate the effects of learning plus possession, and learning alone, relative to a (no information) control group. We find that both social learning and social utility channels have statistically and economically significant effects on investment decisions. Evidence from a follow‐up survey reveals that social learning effects are greatest when the first (second) investor is financially sophisticated (financially unsophisticated); investors report updating their beliefs about asset quality after learning about their peer's revealed preference; and, they report motivations consistent with “keeping up with the Joneses” when learning about their peer's possession of the asset. These results can help shed light on the mechanisms underlying herding behavior in financial markets and peer effects in consumption and investment decisions.     

基于异质价格信念的金融资产泡沫形成机制

假设风险资产未来价格变化由其过去价格变化外推形成,基于现金流股息冲击提出一个新的资产价格泡沫模型研究金融资产泡沫形成机制、提炼其内在特征、获得金融市场稳定发展的相关启示。假设异质价格信念投资者具有常绝对风险规避效用偏好,基于期望效用模型获得基本面投资者和外推型投资者的最优风险资产需求函数;进一步,假设外推型投资者在资产交易过程中部分关注风险资产基本价值,修正其最优风险资产需求函数,在市场出清状态下获得资产价格泡沫模型;基于模型参数设定模拟金融资产泡沫形成机制,并结合金融市场证据分析其内在特征;最后,从投资者异质性和无风险资产收益率层面设定参数值对比讨论影响金融资产泡沫强弱程度的因素。结果表明：在正的现金流股息冲击下,外推交易行为导致金融资产泡沫,且具有滞后性;金融资产泡沫具有典型的三阶段特征,量价齐升是金融资产泡沫产生的显著标志;无风险资产供给是金融资产泡沫的抑制器;投资者结构及其价格信念差异与金融资产泡沫的强弱程度密切相关。研究不但为金融资产泡沫形成机制提供了一个分析框架,而且为金融市场稳定发展提出相关决策参考。     

基于Heston模型时间一致的资产负债管理鲁棒策略

本文在非完备市场框架下，研究了时间一致的鲁棒最优投资组合选择问题。首先，假设金融市场由无风险资产和风险资产构成，其中风险资产的价格过程服从Heston随机波动率模型，且投资者面临一个不可控的外生负债。其次，应用随机最优控制理论，给出并证明了验证定理，建立了相应的拓展Hamilton-Jacobi-Bellman(HJB)方程组，通过求解拓展的HJB方程组，得到了鲁棒均衡投资策略和值函数的显式解。最后，通过数值模拟，给出了模型参数变动对均衡投资策略和效用改善的影响。结果表明：(1) 当风险资产的价格和其波动的相关系数大于零时，股票方差的波动越大，越不利于投资。否则反之。(2) 当风险资产的价格和其波动的相关系数越大时，风险资产的风险就越大，投资者会采取保守的投资策略，减少投资。(3) 负债的波动率变大，投资者会面临更大的负债风险，为了对冲风险，投资者会增加风险资产的投资。(4) 当投资者考虑模型不确定的影响时，采用鲁棒投资策略能显著提高投资者的效用水平。     

Managing Technology Selection and Development Risk in Competitive Environments

Managing development decisions for new products based on dynamically evolving technologies is a complex task, especially in highly competitive industries. Product managers often have to choose between introducing an incrementally better, safe new product early and a superior, yet highly risky, product later. Recommendations for managing such performance vs. time‐to‐market trade‐offs often ignore competitive reactions to development decisions. In this paper, we study how a firm could incorporate the presence of a strategic competitor in making technology selection and investment decisions regarding new products. We consider a model in which an innovating firm and its rival can introduce a new product immediately or pursue a more advanced product for later launch. Further, the firm can reduce the uncertainty surrounding product development by dedicating more resources; the effectiveness of this investment depends on the firm's innovative capacity. Our model generates two sets of insights. First, in highly competitive industries, firms can adopt different technologies and effectively use introduction timing to mitigate the effects of price competition. More importantly, the firm could strategically invest in the advanced product to influence its rival's technology choice. We characterize equilibrium development and investment decisions of the firms, and derive innovative capacity hurdles that govern a firm's choice between the risky and safe alternatives. The effects of development flexibility—where firms might have the option to revert to the safe product if the advanced product fails—are also considered.     

社交网络、 投资者关注与股价同步性

随着以微博、微信为代表的社交网络信息平台在中国的崛起,形成了新媒体时代下信息资讯生成与扩散的完整传播链条,深刻地影响着金融市场参与主体的学习认知习惯、投资决策理念、交易行为模式,最终影响不同金融资产的价格波动规律.本文在新媒体时代情景下,以社交网络信息披露与传播平台为切入点,基于信息关注度、信赖度、更新频率等三层维度,构建社交网络微博信息质量指标体系,研究社交网络信息质量与股价同步性的内在关联关系.研究表明:微博信息质量与股价同步性有着显著的高度负向线性关联性,并且呈现出非线性U型关系.即随着社交网络信息质量水平的提升,股价同步性逐渐降低到达最小值,而后又逐渐提高.研究结论为证明上市公司社交网络微博平台对股价同步性有较强影响力,提供了中国金融市场的证据.