Time-varying betas and the cross-sectional return–risk relation: evidence from the UK

The seminal study by Fama and MacBeth in 1973 initiated a stream of papers testing for the cross-sectional relation between return and risk. The debate as to whether beta is a valid measure of risk was reanimated by Fama and French and subsequent studies. Rather than focusing on exogenous variables that have a larger explanatory power than an asset's beta in cross-sectional tests, the matrix of variances-covariances is assumed to follow a time varying ARCH process. Using monthly data from the UK market from February 1975 to December 1996, the cross-sectional return–risk relations obtained with an unconditional specification for assets’ betas are compared to those obtained when the estimated betas are based on an ARCH model. The approach taken by Pettengill, Sundaram and Mathur, which allows a negative cross sectional return–risk relation in periods in which the market portfolio yields a negative return relative to the risk free rate, was also investigated. These tests are also carried out on samples pertaining to a specific month and on samples from which a particular month is removed. Results suggest that the CAPM holds better in downward moving markets than in upward moving markets hence beta is a more appropriate measure of risk in bear markets.     

Estimating value-at-risk: a point process approach

We consider the modelling of extreme returns in financial time series, and introduce a marked point process model for the exceedances of a high threshold. This model has a self-exciting, Hawkes-process structure in which recent events affect the current intensity of threshold exceedances more than distant ones. Estimates of value-at-risk are derived for real datasets and the success of the estimation method is evaluated in backtests.     

权证发行对标的股票价格风险影响的实证研究

研究权证发行对标的证券价格风险的影响,对研究资本市场的有效性及权证定价等方面具有重要的意义。目前我国已经发行的备兑权证,运用资本资产定价模型(CAPM)和GARCH-M模型,探讨权证的发行时正股的无风险报酬、系统性风险(Beta)和总风险(报酬率波动性)是否有显著影响。实证结果表明,无论是认购权证、认沽权证,还是蝶式权证的发行对正股的无风险报酬、系统性风险的影响基本上均不显著,但对半数以上发行权证的股票的总风险有显著影响。抑制权证市场的投机性,发挥其本身应发挥的价格发现功能、促进股票的流动性、降低股价波动性等的功能,就必须从风险相互对冲的角度,循序渐进地大力发展权证等衍生产品的规模,促进衍生品市场健康、有序地发展。     

The Robustness of the Conditional CAPM with Human Capital

An empirical evaluation is provided of the robustness of theconditional capital asset pricing model (CAPM) with human capitalto explain the cross-sectional variability of security returns.This model has been evaluated in the literature using the growthrate in per capita labor income. This article looks at richermeasures of human capital returns. It develops measures thatincorporate the costs and benefits of educational investment,skill premiums, worker experience, and other relevant featuresof human capital markets. It also considers variables that helpto forecast future human capital returns. We find that someof these richer measures help improve substantially the performanceof the model.     

An examination of predictable risk and return in UK stock returns

This paper examines whether conditional asset pricing models can explain the predictability in UK stock returns using the frameworks of Ferson and Harvey (1999) and Kirby (1998). The paper finds that the domestic Arbitrage Pricing Theory model is able to explain most of the observed time-series predictability in stock returns and tends to perform better than the domestic CAPM in explaining the predictability generated by the predictive instruments. The paper also finds that domestic asset pricing models tends to capture more of the time-series predictability in UK stock returns than international models. However none of the models are able to explain all of the predictability in returns.     

关于小公司效应的分析

小公司效应通常被认为是CAPM的反例，许多人已从实证研究得出了不同的结论。从CAPM的推导公式入手，分析小公司效应与CAPM产生分歧的背景条件，得出：CAPM是一种均衡定价方式。而小公司效应则产生于非均衡市场，这是两矛盾的根源。但两是互融的，而非是排斥的。     

资本资产定价模型有关假设的逻辑分析

资本资产定价模型 (CAPM)假设投资者具有一致预期 ,关于资本资产各项特征的判断完全相同 ,投资者会选择同一个更优的组合。这样 ,所有投资者最终会同时买入 (或卖出 )某一项资产 ,而不存在相应的卖出 (或买入 )者 ,这说明模型假设存在逻辑上的悖论。市场有效性决定了投资者不可能运用历史数据对当前和将来趋势作出准确判断 ,CAPM模型所提供的最优组合只是对过去不同时期优化值的平均 ,有关假设忽视了投资者对资本资产预期价值判断的多样性。投资者不会统一按照CAPM给出的唯一组合来选择风险资产 ,CAPM的最优投资组合可行集实际上是投资组合可能集合的前沿曲线的渐近线 ,而不是前沿曲线的切线。     

流动性风险与资产定价:来自中国股市的证据

LCAPM（基于流动性风险的CAPM模型）是Acharya和Pedersen（2005，Journal of Financial Economics）提出的．它将流动性风险可能影响资产价格的多种方式纳入一个统一的框架。本文利用LCAPM对中国股市进行检验．在该模型中，证券的收益依赖于它的期望流动性及其与收益（包括个股与市场收益）之间的协方差。检验结果发现，我国股市的风险升水在大盘升降区间体现了不同的特征：无论在总区间还是分时段，LCAPM都能更好的拟合资产收益；在控制公司规模之后，效果依然稳健。这说明流动性在我国股市的资产定价上有重要影响。     

A best choice among asset pricing models? The Conditional Capital Asset Pricing Model in Australia

We use Australian data to test the Conditional Capital Asset Pricing Model (Jagannathan and Wang, 1996). Our results are generally supportive: the model performs well compared with a number of competing asset pricing models. In contrast to the study by Jagannathan and Wang, however, we find that the inclusion of the market for human capital does not save the concept of the time‐independent market beta (it remains insignificant). We find support for the role of a small‐minus‐big factor in pricing the cross‐section of returns and find grounds to disagree with Jagannathan and Wang's argument that this factor proxies for misspecified market risk.     

Political and Regulatory Risk in Water Utilities: Beta Sensitivity in the United Kingdom

UK utilities are generally regulated by the periodic setting of a price cap (the RPI-X mechanism). To establish these caps, regulators must determine what returns are appropriate on the capital employed by utilities. This paper addresses the issue of the level of risk inherent in investment in the equity of regulated water utilities in the UK. It uses the techniques of the Kalman Filter to estimate daily betas for the major utilities in the period from privatisation to mid-1999. The paper demonstrates that water utilities' risk is time-variant. It demonstrates, also, that there have been significant political and regulatory influences in the systematic risk faced by water utility shareholders. It finds beta to display little evidence of cyclical variation across the regulatory review cycle. The paper also confirms that significant excess returns have been generated over the history of the privatised water sector and suggests that over-estimation of systematic risk faced by investors in the sector may imply further excess returns in the next regulatory review period.