稳健非参数VaR建模及风险量化研究

参数VaR模型被广泛应用于风险测量中,然而需要给出具体的结构形式,这就容易发生模型错误设定的灾难,使风险计量的精确性易于产生较大偏差。针对参数VaR模型的设定误差问题,本文构建了SQ-ARCH和Nop-Quantile两个非参数VaR模型,诣在提高传统风险计量模型的灵活性、稳定性和准确性。采用稳健的分位数回归方法,得到了计算这两个VaR模型的具体表达式并给出了模型估计的算法和步骤。Monte Carlo模拟发现无论模型正确还是错误设定非参数VaR模型比参数ARCH类VaR模型更稳健。此外,把这两个稳健非参数VaR模型应用于我国股票市场风险量化的实证分析中。研究结果表明稳健非参数VaR模型比参数ARCH类VaR模型度量风险更准确。     

基于极值理论和多元Copula函数的商业银行操作风险计量研究

基于操作风险呈厚尾分布的特征,本文按照巴塞尔协议的要求,采用POT极值模型分别估计了多个操作风险单元的边缘分布,然后用多元Copula函数来刻画这些操作风险单元之间的关联性并计算在险价值。通过对中国商业银行1990-2010年操作风险数据的实证分析表明,Clayton Copula能更好地反映各操作风险单元之间的相关性结构,且采用Copula考虑操作风险相关性下的VaR值要比简单加总下的VaR值减少约32.3%。因此,应用Copula函数计量操作风险相关性,不仅可以提高估计的准确性,还能够达到资产组合的风险分散化效应,减少操作风险资本要求,为商业银行提升盈利能力创造条件。     

基于GARCH-EVT-COPULA模型的外汇投资组合风险度量研究

基于巴塞尔协议和商业银行风险管理新视角,本文运用GARCH-EVT-COPULA模型构建了GARCH-EVT-Gaussian-COPULA和GARCH-EVT-t-COPULA两种方法,对美元、欧元、日元和港元四种人民币汇率的等权重投资组合风险进行了度量,优化了极值分布作为COPULA函数边际分布的多序列超阈值比例确定方法,并与历史模拟法、正态方法、蒙特卡罗方法三种传统方法和单用极值方法度量的VaR进行了比较并作返回检验.结果表明:GARCH-EVT-Gaussian-COPULA扣GARCH-EVT-t-COPULA两种方法符合巴塞尔协议的内部模型法(I--)对商业银行风险管理的要求,而且估计结果优于其他四种方法,其中,GARCH-EVT-Gaussian-COPU LA方法的估计结果比GARCH-EVT-t-COPULA方法更有利于节省商业银行的经济资本.     

度量银行操作风险的POT幂律模型及其应用

本文在极值理论的POT模型基础上,建立了基于分维的POT幂律模型,给出了POT模型的阈值选择的理论解释,还给出了满足尾部分布适合幂律的条件.分析表明,此模型较已有方法能更方便地估计尾部参数,对小样本情形研究厚尾问题提供了新的思路.此外,为计算操作风险损失和的在险价值(VaR)问题,本文引入保险理论里的随机和模型,并给出了计算操作风险在险值的简化公式.     

基于Asymmetric Laplace分布的金融风险度量

金融资产的损益分布具有明显尖峰肥尾和不对称等特征,本文采用非对称拉普拉斯分布来刻画这些风险特征,给出了市场风险VaR和CVaR度量的AL参数法和AL-MC法。选取上证指数、日经225指数及S&P500指数为研究对象,结合各股市的风险特征,给出了VaR和CVaR度量及其返回检验和准确性评价。结果表明,基于AL分布的风险度量模型具有其合理性和适用性,能很好地度量市场风险。     

基于极值理论的风险价值度量

精确度量风险价值(Value-at-Risk,VaR)和以及由此衍生的Expected Shortfall (ES)是对风险管理者的挑战.广泛应用的正态分布不足以描述金融收益的厚尾特征,尤其是风险管理者最为关心的99%或95%分位数.极值理论可以准确地描述分布尾部的分位数.本文利用极值理论计算VaR和ES,并给出它们的误差分析,然后利用深成指数据进行返回检验.两种返回检验方法的结果表明,极值理论方法可以比较精确地度量VaR和ES.     

基于Bayesian-Copula方法的商业银行操作风险度量

本文在对损失分布法分析的基础上,将损失事件划分为内部欺诈、外部欺诈以及违规执行三种类型;引用两阶段分布拟合操作风险的损失强度分布,同时采用贝叶斯理论中的吉布斯抽样来获取参数估计值以减小低频率高损失数据不足带来的误差;考虑到操作风险各损失事件间可能存在的相关性,本文采用Copula函数对操作风险进行整合以获得联合损失分布函数,并计算出不同置信水平下我国商业银行操作风险损失的VaR值与CVaR值.实证研究的结果表明:基于贝叶斯理论的参数估计综合考虑了总体与样本等先验信息,估计出的参数值误差较小;Copula函数的引入与VaR值、CVaR值的测算,能在考虑了损失事件发生概率的同时,估测出操作风险潜在的损失大小,从而可以更准确度量操作风险.     

VaR之下厚尾分布的最优资产组合的收敛性

主要研究在VaR风险度量之下,收益具有厚尾性质的资产的投资组合问题.证明了基于尾部分布二阶展开的最优投资组合收敛于基于尾部分布一阶展开的最优投资组合.因此,对于VaR风险度量之下的最优投资组合问题,如果要求的风险承受水平充分低,则只需要利用尾部分布的一阶展开代替厚尾部分布进行近似计算,就可以达到满意的精度,从而不需要进行复杂的高阶运算.     

股市回报率分布的厚尾性与风险估测模型的绩效探讨

当金融时间序列具有分布的厚尾性、波动的集聚性等特征时,传统的方法将难以胜任对风险的准确度量.除了讨论在厚尾分布下如何应用条件极值与无条件极值来度量风险外,还利用历史模拟、风险矩阵、条件正态模型等方法进行风险值估计,最后运用五项评估指标对各种模型的预测效果进行了比较分析.     

加权复合分位数回归方法在动态VaR风险度量中的应用

风险价值(VaR)因为简单直观,成为了当今国际上最主流的风险度量方法之一,而基于时间序列自回归(AR)模型来计算无条件风险度量值在实业界有广泛应用。本文基于分位数回归理论对AR模型提出了一个估计方法--加权复合分位数回归(WCQR)估计,该方法可以充分利用多个分位数信息提高参数估计的效率,并且对于不同的分位数回归赋予不同的权重,使得估计更加有效,文中给出了该估计的渐近正态性质。有限样本的数值模拟表明,当残差服从非正态分布时,WCQR估计的的统计性质接近于极大似然估计,而该估计是不需要知道残差分布的,因此,所提出的WCQR估计更加具有竞争力。此方法在预测资产收益的VaR动态风险时有较好的应用,我们将所提出的理论分析了我国九只封闭式基金,实证分析发现,结合WCQR方法求得的VaR风险与用非参数方法求得的VaR风险非常接近,而结合WCQR方法可以计算动态的VaR风险值和预测资产收益的VaR风险值。     

Power,authority and legitimacy

Management, human resources, organization, control, leadership, etc., all seem to be just so many euphemisms for power, and this suggests a discourse of management and organization that calls things by their proper name. This paper on the contrary stresses the need to resolve the concept of ‘power’ itself into more differentiated notions, and proposes that clarification may be derived from distinctions once explicit in the vocabulary of Classical antiquity, but lost in modern European languages. It argues that nothing but confusion in thinking about organizations, management and legitimation can result from the failure to recognize that the phenomena this vocabulary identifies and distinguishes are irreducibly different.     

The moderating role of social support in Karasek's job strain model

This paper examines whether social support is a boundary-determining criterion in the job strain model of Karasek (1979). The particular focus is the extent to which different sources of social support, work overload and task control influence job satisfaction, depersonalization and supervisor assessments of work performance. Hypotheses are tested using prospective survey data from 80 clerical staff in a university setting. Results revealed 3-way interactions among levels of support (supervisor, co-worker, non-work), perceived task control and work overload on levels of work performance and employee adjustment (self-report). After controlling for levels of negative affect in all analyses, there was evidence that high levels of supervisor support mitigated against the negative effects of high strain jobs on levels of job satisfaction and reduced reported levels of depersonalization. Moreover, high levels of non-work support and co-worker support also mitigated against the negative effects of high strain jobs on levels of work performance. The results are discussed in terms of the importance of social support networks both at, and beyond, the work context.     

Job insecurity, coping resources and personality dispositions in occupational strain

This paper presents research on the relationships between the work-related stressor of perceived job insecurity and various indicators of occupational strain, taking into account employees' personality dispositions (trait negative and positive affectivity) and coping resources. Respondents were 222 Australian public servants surveyed during organizational restructuring that involved downsizing and threat to job certainty. The research was formulated within an adaptation of Osipow, Doty, and Spokane's (1985) framework of stress-strain-coping that included the possible direct as well as moderating effects of personality dispositions in reporting occupational strain (Parkes, 1990). Findings from hierarchical regression analyses indicate consistent significant independent effects of personality dispositions, coping resources and perceived job insecurity on various indicators of strain. There was also support for the moderating roles of negative affectivity and self-care in the relation between perceived job insecurity and physical strain. Implications for the role of dispositional factors, especially negative affectivity, and the utility of various coping resources in accounting for occupational strain in times of threatened job security are discussed.     

Dermal Uptake of 18 Dilute Aqueous Chemicals: In Vivo Disappearance‐Method Measures Greatly Exceed In Vitro‐Based Predictions

Average rates of total dermal uptake (K_up) from short‐term (e.g., bathing) contact with dilute aqueous organic chemicals (DAOCs) are typically estimated from steady‐state in vitro diffusion‐cell measures of chemical permeability (K_p) through skin into receptor solution. Widely used (“PCR‐vitro”) methods estimate K_up by applying diffusion theory to increase K_p predictions made by a physico‐chemical regression (PCR) model that was fit to a large set of K_p measures. Here, K_up predictions for 18 DAOCs made by three PCR‐vitro models (EPA, NIOSH, and MH) were compared to previous in vivo measures obtained by methods unlikely to underestimate K_up. A new PCR model fit to all 18 measures is accurate to within approximately threefold (r = 0.91, p < 10^?5), but the PCR‐vitro predictions (r > 0.63) all tend to underestimate the K_up measures by mean factors (UF, and p value for testing UF = 1) of 10 (EPA, p < 10^?6), 11 (NIOSH, p < 10^?8), and 6.2 (MH, p = 0.018). For all three PCR‐vitro models, log(UF) correlates negatively with molecular weight (r² = 0.31 to 0.84, p = 0.017 to < 10^?6) but not with log(vapor pressure) as an additional predictor (p > 0.05), so vapor pressure appears not to explain the significant in vivo/PCR‐vitro discrepancy. Until this discrepancy is explained, careful in vivo measures of K_up should be obtained for more chemicals, the expanded in vivo database should be compared to in vitro‐based predictions, and in vivo data should be considered in assessing aqueous dermal exposure and its uncertainty.     

Systems Resilience for Multihazard Environments: Definition,Metrics, and Valuation for Decision Making

The United Nations Office for Disaster Risk Reduction reported that the 2011 natural disasters, including the earthquake and tsunami that struck Japan, resulted in $366 billion in direct damages and 29,782 fatalities worldwide. Storms and floods accounted for up to 70% of the 302 natural disasters worldwide in 2011, with earthquakes producing the greatest number of fatalities. Average annual losses in the United States amount to about $55 billion. Enhancing community and system resilience could lead to massive savings through risk reduction and expeditious recovery. The rational management of such reduction and recovery is facilitated by an appropriate definition of resilience and associated metrics. In this article, a resilience definition is provided that meets a set of requirements with clear relationships to the metrics of the relevant abstract notions of reliability and risk. Those metrics also meet logically consistent requirements drawn from measure theory, and provide a sound basis for the development of effective decision‐making tools for multihazard environments. Improving the resiliency of a system to meet target levels requires the examination of system enhancement alternatives in economic terms, within a decision‐making framework. Relevant decision analysis methods would typically require the examination of resilience based on its valuation by society at large. The article provides methods for valuation and benefit‐cost analysis based on concepts from risk analysis and management.     

Defining Spirituality of Work

There is a current surge of writings on spirituality and related topics. For instance, Woodward (1997) has pointed out that since Thomas Moore's publication of Care of the Soul in 1994 there have been nearly 800books published with the word soul in the title. These run all the way from Chicken Soup for theWoman's Soul (Canfield et al., 1996) to A Guide to Liberating YourSoul (Barrett, 1995). Spirituality of work is a big part of this surge. Definitionsof spirituality of work seem to vary widely. Bowman (1998, p. 8) in his `reviewof the phenomenon of spirituality of work' found `Definitions of the term spirituality in the context of the Spirituality of Work troublesome and particularly subjective. Many writers do not even attempt definitions.' The purpose of this article is to review the concept of spirituality of work in its historical and current use and to propose a comprehensive definition.     

A new lease for life? The return of vitalism in management and organization studies

This paper starts from a growing interest in the concept of concern, lived experience or “inhabiting” as part of the so-called “affective turn”. My main argument is that the notion of concern cannot be thought or understood without the concept of life. The concept of life, however, is somewhat of a taboo topic in the social sciences. I hold, nevertheless, that in order to reflect on their assumptions and to define concern for their own studies, scholars need to think about life and make a choice regarding the various approaches that can be taken. I therefore present and compare four vitalist approaches: romanticism and Lebensphilosophie, vitalism as ethos and pathos, neuroecosociality as well as vitalism as becoming.     

Consequences of work-family conflict on employee well-being over time

The effects of work-family conflict on the well-being of a diverse sample of 342 non-professional employees from the greater Los Angeles area were examined. Data were collected at two points in time, and a rigorous research design was employed. The effects of self-report bias were considered by controlling for social desirability bias, and by collecting two sources of data (i.e. self-reports and co-workers reports). The results revealed that work-family conflict predicted employee well-being over and above social desirability bias. In addition, analyses were consistent when both self-reports and co-workers reports were utilized. Finally, work-family conflict was a longitudinal predictor of employee's positive well-being. Both cross-sectional and longitudinal analyses were consistent across self-reports and co-worker reports.     

Policy Goals for Health and Safety

Health management and safety regulation are separate disciplines but share the aim to extend expectancy of life in good health. The need to improve cost-effectiveness calls for their co-ordinated management according to a unified rationale. Three guiding principles of accountability, demonstrable net benefit and a uniform measure of performance, have been laid out in Canada by the Joint Committee on Health and Safety. They call for open accounting in terms of (health-related quality-adjusted) life expectancy. The principles are utilitarian in format but, it is argued, inequity is naturally diminished in the process of optimizing cost-effectiveness through maximum marginal returns. Comments are made on practical implementation. The need for public consent in practice calls for two additional principles reflecting fair procedure and sovereignty of the citizens. It is concluded that public health and safety measures should be surveyed, documented for cost-effectiveness and prioritized for improvement.