土地资源错配与经济波动的空间溢出效应实证分析

文章构建了一个采用时变引力空间权重矩阵的空间自滞后模型(SLX),探讨土地资源错配对经济波动的空间溢出效应。实证结果表明:本地区土地资源错配能够减缓邻近地区的经济波动,即土地资源错配会对经济波动存在负向空间溢出效应;土地资源错配对经济波动的负向空间溢出效应主要通过降低密度边际波动来实现。进一步研究发现,在三类不同等级城市间,土地资源错配对经济波动的空间溢出效应不尽相同:在自上而下的空间溢出效应中,并不是每类高等级城市都对低等级城市存在空间溢出效应,而在自下而上的空间溢出效应中,每类低等级城市都对高等级城市存在空间溢出效应,同等级城市间的空间溢出效应则并不显著。     

时变环境下选址问题的一个启发式算法

配送中心选址作为物流管理中的一个重要研究问题受到广泛重视。然而,文献中所涉及的选址模型大都是静态的,即沿一条路径行进时所需的成本(或时间)是与出发时间无关的函数。但在实际生活中,它往往是会随时间的变化而变化的,这类问题被称为时变环境下的选址问题。文中讨论了时变环境下的单配送中心到多个零售点带容量约束的选址问题。由于该问题是NP-完备的,我们给出了一个启发式算法。     

SAD效应：一个基于时变风险价格的条件CAPM的解释

很多实证研究都证明季节性情绪混乱(SAD)与股指收益有明显联系。本文研究了这种SAD效应能否用一个包含允许时间变化的风险价格的资产定价模型去捕捉它的存在。本文利用上证综指的日收盘数据得到的初始和超额收益率以及SAD和FALL变量,利用修正的GRACH-M模型进行了分析,认为条件CAPM可以捕捉SAD效应。这与由于日照时间变化而导致的投资者风险承受能力变化进而影响收益的认识相符合。     

基于copula的投资组合选择模型的研究

本文首先介绍了投资组合理论与copula,然后给出基于概率的收益率等定义,建立基于概率的收益率的投资组合选择模型并给出具体解法,接着通过选取上证领先指数与深证领先指数2004年9月1日至2006年5月26日的日收盘数据进行实证分析,发现在收益率(基于概率的收益率)一定的情况下,通过投资组合可以降低风险。pápápá     

Portfolio optimization with CVaR under VG process

Formal portfolio optimization methodologies describe the dynamics of financial instruments price with Gaussian Copula (GC). Without considering the skewness and kurtosis of assets return rate, optimization with GC underestimate the optimal CVaR of portfolio. In the present paper, we develop the approach for portfolio optimization by introducing Lévy processes. It focuses on describing the dynamics of assets’ log price with Variance Gamma copula (VGC) rather than GC. A case study for three Indexes of Chinese Stock Market is performed. On application purpose, we calculate the best hedge positions of Shanghai Index (SHI), Shenzhen Index (SZI) and Small Cap Index (SCI) with the performance function CVaR under VG model. It can be combined with Monte Carlo Simulation and nonlinear programming techniques. This framework is suitable for any investment companies.     

Sorting, Firm Characteristics, and Time-varying Risk: An Econometric Analysis

We show that sorting reveals the time-varying market risk exposuresof the firm-specific investment opportunity set. Sorting onthe basis of firm characteristics uncovers information on firm-specificdistress or growth, and this leads to more efficient estimationof conditional risk sensitivity. We demonstrate the effectivenessof the sorting methodology with an empirical exercise that teststhe conditional capital asset pricing model (CAPM). When measuredproperly using sorting and firm characteristics, conditionalbetas, along with size and the book-market ratio, are significantdrivers of expected returns.     

信用风险度量及其组合管理中的相关性研究——Copula函数的引进

综述了从传统过渡到现代的信用风险度量方法,并比较了它们的特点.提出组合管理思想是信用风险管理的方向,组合的相关性问题是研究重点.而Copula函数具有描述非线性相关的优势,使用Copula函数可以更加精确地度量信用风险.     

Evolving Market Efficiency with an Application to Some Bulgarian Shares

With new technically advanced methods and computers at our disposal, the efficient market hypothesis is once again being debated. At the same time, we are witnessing an unprecedented growth in both existing and new financial markets. These new markets are often in economies which have just recently embraced free market economics; we term these stock markets infant markets. Such stock markets are obviously not efficient in allocating the supply of savings to productive capital. We do not test whether or not these infant markets are informationally efficient, but instead examine whether and how they are becoming more efficient. We propose modelling the excess returns of individual securities using a multi-factor model with time-varying coefficients and generalised auto-regressive conditional heteroskedastic (GARCH) errors. If the markets are becoming more informationally efficient or the agents are learning, we would expect this to manifest itself as the time-varying coefficients becoming more stable as time increases. We test our model using data on four Bulgarian shares. First, we estimate an AR(2) model and a GARCH-M(1,1) model for the shares. Then, we estimated our AR(2) model with time varying coefficients and GARCH type errors. We find varying levels of efficiency and varying speeds of movement towards efficiency within our sample of four shares. This revised version was published online in July 2006 with corrections to the Cover Date.     

我国股市行业时变β系数研究

本文主要考察了我国股市13个行业的β系数及信息的影响。研究发现市场信息和行业信息对β系数都有影响,但影响的方向和大小因行业而异。进而对这些行业的β系数的信息非对称效应产生原因进行考察。仅有部分行业的β系数的信息非对称效应可由市场利空消息或行业利空消息解释。     

变时滞循环神经网络模型的全局指数稳定性

利用Brouwer不动点定理，推广的Halanay时延微分不等式及Dini导数，讨论了具有变时滞循环神经网络模型的平衡点的存在性和全局指数稳定性，在不要求激活函数连续可导的条件下，得到了非常简单实用的判别条件。