中国股市β系数稳定性研究

β系数是证券或证券组合与市场相互关联的一个概念和参数,它是衡量证券系统风险的重要指标,β系数的稳定性也一直是学术界和投资者特别关注的焦点。本文通过中国股票市场的31个行业数据的研究,得到中国股市样本β值在单位β值(1.00)附近上下波动并呈正态分布;也可以得到组合的β系数还是有较好的稳定性结论。     

犹太社会活动家莫尔杰哈伊·奥尔默特述评

莫尔杰哈伊·奥尔默特是著名的犹太社会活动家、哈尔滨贝塔运动先驱。1927年曾就读于哈尔滨工业大学,并在就读期间积极参加了哈尔滨贝塔青年组织的活动,为了筹集回国路费,赴双城堡中学执教一年。1933年回归以色列,为以色列建国做出了卓越贡献,并创建了阿米卡姆莫沙夫。奥尔默特作为原居哈尔滨犹太人,是中犹友谊发展的历史见证人。     

Fueling agricultural growth in India: Some reflections

Indian agriculture is experiencing under-performance despite increased attention given to it in the recent past. This paper analyzes the disparities in agricultural growth across Indian states and explores the determinants of agricultural growth, using Panel Corrected Standard Error approach. Analysis using beta convergence shows that the disparities across the state's agricultural growth are narrowing down for the period 1980–1981 to 2011–2012. However, to stimulate growth in the states where agriculture is lagging behind, a higher emphasis on increasing the area under irrigation, expenditure on agricultural research, area under fruits and vegetables, number of regulated markets, length of roads, cold storage facilities and institutional credit for investment purposes is needed. Private sector should be involved in public–private-partnership mode for improving the infrastructure in this sector.     

Moments of Compound Mixed Poisson Distributions

Recursive formulae are derived for the evaluation of the moments and the descending factorial moments about a point n of mixed Poisson and compound mixed Poisson distributions, in the case where the derivative of the logarithm of the mixing density can be written as a ratio of polynomials. As byproduct, we also obtain recursive formulae for the evaluation of the moments about the origin, central moments, descending and ascending factorial moments of these distributions. Examples are also presented for a number of mixing densities.     

Robust estimation with flexible parametric distributions: estimation of utility stock betas

The distributions of stock returns and capital asset pricing model (CAPM) regression residuals are typically characterized by skewness and kurtosis. We apply four flexible probability density functions (pdfs) to model possible skewness and kurtosis in estimating the parameters of the CAPM and compare the corresponding estimates with ordinary least squares (OLS) and other symmetric distribution estimates. Estimation using the flexible pdfs provides more efficient results than OLS when the errors are non-normal and similar results when the errors are normal. Large estimation differences correspond to clear departures from normality. Our results show that OLS is not the best estimator of betas using this type of data. Our results suggest that the use of OLS CAPM betas may lead to erroneous estimates of the cost of capital for public utility stocks.     

Out-of-sample density forecasts with affine jump diffusion models

We conduct out-of-sample density forecast evaluations of the affine jump diffusion models for the S&P 500 stock index and its options’ contracts. We also examine the time-series consistency between the model-implied spot volatilities using options & returns and only returns. In particular, we focus on the role of the time-varying jump risk premia. Particle filters are used to estimate the model-implied spot volatilities. We also propose the beta transformation approach for recursive parameter updating. Our empirical analysis shows that the inconsistencies between options & returns and only returns are resolved by the introduction of the time-varying jump risk premia. For density forecasts, the time-varying jump risk premia models dominate the other models in terms of likelihood criteria. We also find that for medium-term horizons, the beta transformation can weaken the systematic effect of misspecified AJD models using options & returns.     

Models for stock returns

Historically, the normal variance model has been used to describe stock return distributions. This model is based on taking the conditional stock return distribution to be normal with its variance itself being a random variable. The form of the actual stock return distribution will depend on the distribution for the variance. In practice, the distributions chosen for the variance appear to be very limited. In this note, we derive a comprehensive collection of formulas for the actual stock return distribution, covering some sixteen flexible families. The corresponding estimation procedures are derived by the method of moments and the method of maximum likelihood. We feel that this work could serve as a useful reference and lead to improved modelling with respect to stock market returns.     

Beta射线技术在颗粒物中的应用研究

本文通过对于Beta射线技术的分析得到一种可以用于环境空气颗粒物PM2.5连续监测过程的技术,并对该技术在不同条件下进行测试,通过所得到的数据得出该技术的适用性和技术局限性。     

In search of beta

Despite its limitations, the CAPM is a popular asset pricing model. However, the estimation of beta in the CAPM is affected by the choice of the returns frequency and firm characteristics. This study undertakes a detailed examination of the evidence for the UK and we find that the differences in beta computed from returns of various frequencies are related to size, liquidity, book-to-market and to some degree, opacity factors. One area where our conclusions might have important implications is in the regulatory use of the CAPM. Our results imply that low frequency beta estimates should, in most cases, be preferred to high frequency beta estimates.     

Equilibrium compound distributions and stop-loss moments

A convolution representation is derived for the equilibrium or integrated tail distribution associated with a compound distribution. This result allows for the derivation of reliability properties of compound distributions, as well as an explicit analytic representation for the stop-loss premium, of interest in connection with insurance claims modelling. This result is extended to higher order equilibrium distributions, or equivalently to higher stop-loss moments. Special cases where the counting distribution is mixed Poisson or discrete phase-type are considered in some detail. An approach to handle more general counting distributions is also outlined.