中国证券市场中Beta系数的存在性及其相关特性研究

本文认为,中国证券市场存在资本资产定价模型中描述的Beta系数,本文发现,使用不同市场收益率的算法计算出来的Beta系数有着显著的差异。因此,存在以不同的方法计算得到的Beta系数,在相同的研究过程中得出不相同的结果的情况可能会出现。本文的研究结果证实了这样一个事实:在中国证券市场,至少是在本文研究的时间区间段,CAPM模型是成立的。本文还发现,中国证券市场中Beta系数并不存在显著的行业差异,但是在按照是否被纳入计算成份类指数的标准将股票进行分类,即分为成份股和非成份股,这两大类股票的Beta系数存在显著的差异;本文还发现,在中国证券市场中,几乎不存在支持资本资产定价模型中的无风险收益率的参数。     

深圳股市时变Beta、条件CAPM实证研究

建立Engle(2002)提出的动态条件相关多元GARCH模型计算深圳股市诸行业指数2001/07/02～2005/07/15期间的时变Beta系数,进而对系统风险Beta系数与收益的关系进行传统的检验和由Pettengill et al.(1995)提出的条件检验,并且探讨了非系统风险、总风险在资产定价中的作用.研究结果表明,Beta与收益间不存在传统的无条件相关关系;部分行业指数的Beta系数与收益符合条件相关关系:当超额市场收益大于0(上市场)时,Beta和收益正相关;当超额市场收益小于0(下市场)时,Beta与收益负相关.但对大多数指数而言,Beta与收益仅在下市场时呈显著的负相关关系.同时非系统风险以及总风险均得到了补偿,表明深圳股市的投资者并没有充分分散化其投资,政府应大力发展机构投资者.     

内生性回收率与信用风险度量研究

在信用风险模型中,外生性回收率的设定会忽略回收率对损失分布尾部的影响,而且会导致潜在的模型风险。本文将因子扩散过程引入结构信用风险模型,获得了回收率和违约概率之间的内在关系,利用Monte Carlo模拟方法数值分析了预期回收率对违约概率和资产价值波动率的依赖性,结果表明预期回收率与违约率之间具有很强的负相关关系,而且这种相关关系会受到债务人资产价值波动率的正向影响。在内生性回收率下,推导了信用损失的概率分布,计算了信用风险的Credit-VaR和ETF指标。最后利用市场数据检验了内生回收率信用风险模型的有效性,结果表明该模型可以很好的描述历史违约率和回收率的变化过程。     

基于SV-SGED模型的动态VaR测度研究

本文针对金融资产收益展现出“有偏”及“厚尾”分布特征,引入有偏广义误差分布（SGED）来描述资产收益,继而提出SV-SGED模型对资产收益波动率建模,并以此来测度动态风险值（VaR）,进而采用后验测试技术对风险测度模型的精确性进行检验。同时,为了估计SV模型的参数,提出基于有效重要性抽样（EIS）技巧的极大似然（ML）估计方法。最后,给出了基于上证综合指数的实证研究。结果表明,SV-SGED模型比正态分布假定下的SV（SV-N）和广义误差分布假定下的SV（SV-GED）模型具有更好的波动率描述能力,SV-SGED模型展现出比SV-N和SV-GED模型更优越的风险测度能力。     

沪深300股指套期保值及投资组合实证研究

采用协整等分析方法,对沪深300股指标的进行投资组合研究,给出了动态投资组合的操作方法,结果表明基于模型选择的投资组合具有较好的系统均衡性、较小的风险及较高的收益率.同时对静态选择的50只股票组合、基于模型动态选择的17只股票的投资组合以及单个股票投资进行沪深300股指期货套期保值比的模拟实证分析,采用OLS回归模型估计法、双变量向量自回归模型方法、基于协整关系的误差修正模型方法、简化的误差修正模型方法,对不同模型方法下的套期保值比进行实证研究,最后对利用沪深300股指期货进行套期保值的有效性给出评价.     

大规模同质不良资产组合回收率定价研究

处置不良资产是我国金融业改革和发展的重要问题,大规模批量处置不良贷款是处置不良资产的首选方法之一.不良贷款组合的回收率分布,是不良贷款组合定价的基础.针对不良贷款回收率的双峰分布特性,将不良贷款分为低峰回收贷款和高峰回收贷款,证明了不良贷款组合的回收率收敛于低峰回收率和高峰回收率的条件期望之和.基于信用风险结构模型,进一步证明了高峰回收率条件期望的正态逆变换与低峰回收比率的正态逆变换之间存在线性关系.由于对低峰回收贷款易于判断,很容易估计低峰回收比率,因而可以通过线性回归估计出高峰回收率条件期望,这样就给出了不良贷款组合的整体回收率估计模型.基于这一模型,还给出了估计不良贷款回收率的分位数的计算方法,该方法实际上是VaR方法的推广.     

双长记忆GARCH族模型的预测能力比较研究——基于沪深股市数据的实证分析

GARCH族模型在金融风险的度量中有着广泛的应用。在考虑股市收益率和波动率序列双长记忆性的基础上,基于上证综合指数和深圳成份指数的日收盘价序列,从证券投资风险量化的角度,引入受险值VaR和相对正确符号指标PCS作为模型预测误差衡量指标,比较分析了双长记忆GARCH族模型在不同分布假设情况下的的拟合与预测精度。结果显示:偏t分布能较好描述沪深股市的厚尾特征;在较小的VaR水平下ARFIMA(2,d₁,0)-FIAPARCH(1,d₂,1)-skt模型对股市波动风险具有较强的预测能力,而ARFIMA(2,d₁,0)-HYGARCH(1,d₂,1)-skt对股市的涨跌趋势具有较强的预测能力。     

基于ARIMA-GARCH模型和极值理论的中国股市风险价值度量

以极值理论为基础的风险值度量方法是最近发展起来的最为有效的方法之一,但在传统的单纯采用极值理论的建模过程中对误差项假定为独立同分布的白噪声过程,会对应用极值理论估算风险价值产生一定误差。本文以上证指数和深证成指为例,利用ARIMA-GARCH模型捕获股票收益序列中的自相关和异方差现象,对该模型中残差的条件分布的合理假定进行了实证分析比较,然后利用极值理论对经过ARIMA-GARCH模型筛选过的残差进行极值分析,估算风险价值。     

非极端回收不良贷款的回收率预测研究

本文依托Loss Metric数据库,对非极端回收不良贷款的回收率预测模型进行了研究。文章通过对非极端回收不良贷款的回收率进行Beta-正态变换和Logit变换,结合影响不良贷款回收率的众多因素,进行了从简单到复杂、从单笔贷款债务人到多笔贷款债务人的逐级建模,并剖析了影响回收率的各个因素。实证结果表明,单笔贷款债务人的回收率模型可作为多笔贷款债务人回收率预测的基准;从单笔贷款债务人模型中可以更直观的分析各个不同的变量对回收率的影响。     

中国货币供应量与GDP多项式分布正负反馈预测模型研究

采用经济计量学中无约束多项式分布滞后模型,研究了利用1952年～2000年间年度货币供应量M2预测相应年度GDP的正反馈模型,在每个观测点1955年～2000年处的预测精度高达10-8以上,几乎无误差.同时,在相同时期内还给出了利用年度GDP数据预测年度货币供应量M2的负反馈模型,在每个观测点处的预测精度高达10-8以上,几乎无误差.可见,货币供应量M2与经济增长的正负反馈模型拟合效果相当好,而从模型的其它指标看,完全可应用于实际的预测,这为利用常规的年度GDP数据获取较为准确的货币供应量M2预测数据提供了新的思路和途径.     

新产品分销密度的动态优化

本文讨论了新产品上市过程中的分销密度的动态诊断问题,旨在识别分销密度是否偏离最优的动态演化路径,进而帮助厂商获取最大化的新产品利润。从控制理论模型构建的角度出发,分销密度被视为控制变量,新产品销售量被视为状态变量,并基于泛函极值的动态规划方法,推导了分销密度的最优路径解。然后,以两组家电新产品的市场销售数据为样本,进行了应用算例分析。研究结果表明,本文推导的分销密度最优路径解,不仅能够有效提升制造商的销售利润,而且其形态会随着参数取值的差异,发生明显的变化。当分销密度导数对销售量的影响系数不断增大时,分销密度的最优路径会逐步收敛到一条直线。所以,在假设条件成立的前提下,本文的研究结果揭示出分销密度的动态演化规律,进而为制造商的新产品分销密度规划提供定量的决策依据。     

SEARCH INTENSITY,DIRECTED SEARCH,AND THE WAGE DISTRIBUTION

We propose a search equilibrium model in which homogeneous firms post wages along with a vacancy to attract job seekers while homogeneous unemployed workers invest in costly job seeking. The key innovation relies on the organization of the search market and the search behavior of the job seekers. The search market is continuously segmented by wage level, individuals can spread their search investment over the different submarkets, and search intensity has marginal decreasing returns in each submarket. We demonstrate the existence of a nondegenerate equilibrium wage distribution. The density of this wage distribution is increasing at low wages and decreasing at high wages. The distribution can be right‐tailed, and, under additional restrictions, is hump‐shaped. Our results are illustrated by an example generating a Beta wage distribution.     

C2C环境中顾客重复购买行为的实证与建模

通过分析C2C商家的交易记录,发现单个商家的顾客重复购买次数呈幂律分布,这与重复购买理论以往得到的购买次数为负二项分布的结论不同.基于C2C交易的实际情况,建立了具有购买强化效应的购买概率模型,模型很好的解释了顾客重复购买率呈幂律分布的现象.实证和模型表明,C2C环境中,顾客购买次数的分布具有很长的尾部,大量顾客有低的购买次数,而少数顾客有很高的重复购买次数;模型还揭示了巨大的潜在顾客数量和顾客多次购买的强化效应是造成重复购买分布呈幂律形式的重要原因.     

Modelling multibrand consumption

In this article a model for the multibrand consumption of fast moving non-durable consumer goods is presented. The model is derived by the mixing of a multinomial distribution (representing the brand consumption probabilities of an individual household) with the continuous multivariate Beta (Dirichlet) distribution (which allows for differences between households). The core of the analysis involves the use of complete bivariate tables. The model is shown to provide an adequate representation of a set of consumption data and to satisfactorily estimate the various brand market shares.     

基于Supply-Hub的生产与配送协同模式研究

本文建立了需求随机情况下的基于Supply-Hub的两供应商、单制造商生产与配送协同决策模型,通过与没有Supply-Hub的两供应商-单制造商生产与配送协同决策模型进行对比,证明了Supply-Hub的协同功能能够降低各供应商的成本、制造商的总成本和供应链的总成本。最后通过参数分析,揭示了需求的不确定性对基于Supply-Hub的生产与配送协同模式的影响,研究结果表明：需求不确定性越高,Supply-Hub模式的优势表现的越明显,而且即使需求的不定性非常高,Supply-Hub也可以将配送批量控制在一定范围内;当需求的不确定性超过一定范围时,供应商会采用多批次、小批量的配送方式给Supply-Hub配送零部件来规避风险。     

LIBERALIZING A DISTRIBUTION SYSTEM: THE EUROPEAN CAR MARKET

We quantify the competitive effects of liberalizing the selective and exclusive distribution system in the European car market, based on a model of oligopoly pricing with differentiated products. We consider two possible competitive effects from liberalization: (i) the creation of international intrabrand competition (cross‐border trade), which will result in a reduction of international price discrimination; and (ii) a possible cumulative effect arising from a strengthening of national intrabrand competition, which would result in reduced double marginalization. We find that the reduction in international price discrimination mainly redistributes consumer gains across countries; it has a positive but modest effect on total welfare. If liberalization also has the cumulative effect of reducing double marginalization, the welfare effects are much higher. Finally, we find that the effects of liberalization on the manufacturers' profits are either small or positive. This finding implies that international price discrimination, and softening competition through a double marginalization mechanism, should not be interpreted as main profit motives for the previous distribution system, but only as unintended side effects. Hence, the industry rationale for maintaining the previous distribution system should be sought in other areas. (JEL: F15, L42)     

The Beta Poisson Dose-Response Model Is Not a Single-Hit Model

The choice of a dose-response model is decisive for the outcome of quantitative risk assessment. Single-hit models have played a prominent role in dose-response assessment for pathogenic microorganisms, since their introduction. Hit theory models are based on a few simple concepts that are attractive for their clarity and plausibility. These models, in particular the Beta Poisson model, are used for extrapolation of experimental dose-response data to low doses, as are often present in drinking water or food products. Unfortunately, the Beta Poisson model, as it is used throughout the microbial risk literature, is an approximation whose validity is not widely known. The exact functional relation is numerically complex, especially for use in optimization or uncertainty analysis. Here it is shown that although the discrepancy between the Beta Poisson formula and the exact function is not very large for many data sets, the differences are greatest at low doses--the region of interest for many risk applications. Errors may become very large, however, in the results of uncertainty analysis, or when the data contain little low-dose information. One striking property of the exact single-hit model is that it has a maximum risk curve, limiting the upper confidence level of the dose-response relation. This is due to the fact that the risk cannot exceed the probability of exposure, a property that is not retained in the Beta Poisson approximation. This maximum possible response curve is important for uncertainty analysis, and for risk assessment of pathogens with unknown properties.     

AEPD、AST和ALD分布下金融资产收益率典型事实描述与VaR度量

金融资产收益率分布具有"尖峰"、"肥尾"、"有偏"、"非对称"等典型事实,传统的正态分布、t分布、SKST分布无法完全描述这些特征,影响了以收益率分布设定为基础之一的参数法VaR模型度量的效果。近年来,理论界提出了AEPD、AST、ALD等分布来改善对金融资产收益率分布的描述。本文以沪深300指数为例,比较和分析了这些分布对金融资产收益率典型事实特征的描述及其在VaR度量效果上的差异。研究表明并非捕捉金融资产收益率分布典型事实越多的模型测度风险的效果越好:AEPD、 AST、ALD分布能较好地描述金融资产收益率的典型特征,但是在风险度量效果上却只能证明AEPD、AST分布绝对优于正态分布,而与SKST分布相比无明显差异; ALD分布在度量空头VaR时效果甚至比正态分布更差,但在计算低分位水平下的多头VaR值时却明显优于其他分布。     

The Monotonicity of Individual and Market Demand

This paper studies the monotonicity of individual and market demand with the aid of the indirect utility function. We identify sufficient (and in a sense, necessary) conditions on an agent's indirect utility which will guarantee that he has a monotonic demand function. Our conditions also point to a natural way of extending the result of Hildenbrand (1983). Hildenbrand showed that market demand is monontonic if the income distribution has a downward sloping density, even though individual agents' demand function might violate monotonicity. Using the indirect utility function, we introduce a measure of violations of individual monotonicity that allows us to identify a larger class of density functions that will generate a monotonic market demand.