媒体情绪传染与分析师乐观偏差——基于机器学习文本分析方法的经验证据

本文利用2013～2017年上市公司的百度新闻报道作为文本,运用机器学习文本分析方法测算情绪倾向得分,考察了媒体情绪对分析师预测行为的影响及其传染机制与风险后果。研究发现:(1)媒体乐观情绪会显著正向影响分析师盈利预测的乐观偏差度;(2)媒体情绪通过"分析师有限关注"与"投资者情绪"两条路径来影响分析师预测的乐观倾向;(3)分析师乐观情绪和媒体乐观情绪均会加剧股价波动及尾部风险,且分析师乐观情绪是媒体情绪影响股价波动的传导路径;(4)明星分析师与非明星分析师均会受到媒体情绪的感染,前者理性程度相对更高但其行为对股价波动冲击更为明显。本研究对于规范媒体行为,矫正分析师过度乐观偏差,合理引导理性投资具有重要意义。     

连锁董事和股价同步性波动:基于网络视角的考察

在中国上市公司中普遍存在连锁董事的背景下,从公司透明度和趋同性两方面分析连锁董事对公司股价与市场波动之间的关系,采用实证方法进行检验,并进一步分析连锁董事对股价同步性波动的作用机制。以2003年至2010年中国上市公司为样本构建纵列截面数据,借鉴网络分析方法,采用居中中心度、中介中心度和向量中心度度量公司的连锁董事。实证结果表明,拥有连锁董事公司的股价同步性波动更高;在网络中镶嵌越紧密的公司,其股价波动和市场波动更一致。进一步研究还发现,在大公司和国有控制公司中,连锁董事通过降低公司透明度增加股价同步性波动;在小公司和非国有控制公司中,连锁董事通过增加公司间的趋同性增加股价同步性波动。研究结论对提高资本市场的效率有重要的政策意义。     

基于模拟抽样的长期异常收益率度量方法的比较分析

首先分析了CAR、BHAR和TBHAR模型用于度量股价长期异常收益率的差异及适用性,随后利用我国深沪两市A股市场的数据用随机模拟抽样的方法比较了三种度量方法的度量效果,指出TBHAR模型在度量长期异常收益率方面的可取性.     

沪、深股票市场与香港股票市场的溢出效应——基于发布“港股直通车”方案前后的比较分析

本文以沪、深、港三地股票市场的数据为样本,用VAR模型和二元GARCH模型重点研究"港股直通车"事件是否对港市与沪、深股市的收益率及波动溢出关系有显著影响.研究结果表明,"港股直通车"公布之前,港市与沪、深股市间不存在任何方向的收益率溢出效应,但存在单向波动溢出效应;"港股直通车"公布之后.港市与沪、深股市间不仅存在单向收益率溢出效应,港市与沪市间还存在双向波动溢出效应,与深市间则存在单向波动溢出效应.     

R2与股价中的信息含量度量

基于新古典金融经济学的分析框架,在全面分析信息、噪声、股价波动以及波动同步性(R2)相互关系的基础上,从理论角度提出了股价中信息含量与R2之间可能存在倒U字型关系的假说;将机构持股比例作为股价中信息含量的代理变量,并利用我国A股市场2004年度市场交易数据进行了标准的计量分析,实证结果证实了上述假说.从而表明:在我国A股市场上进行公司层面的分析时,如果用R2直接作为股价中信息含量的度量,可能会混淆信息与噪声对个股股价波动的影响,因为较小的R2既可能是由资本化进了更多的个股信息所引起的,也可能源于更大的噪声对个股股价所产生的影响.     

R~2与股价中的信息含量度量

基于新古典金融经济学的分析框架,在全面分析信息、噪声、股价波动以及波动同步性(R2)相互关系的基础上,从理论角度提出了股价中信息含量与R2之间可能存在倒U字型关系的假说;将机构持股比例作为股价中信息含量的代理变量,并利用我国A股市场2004年度市场交易数据进行了标准的计量分析,实证结果证实了上述假说.从而表明:在我国A股市场上进行公司层面的分析时,如果用R2直接作为股价中信息含量的度量,可能会混淆信息与噪声对个股股价波动的影响,因为较小的R2既可能是由资本化进了更多的个股信息所引起的,也可能源于更大的噪声对个股股价所产生的影响.     

中国股票市场价格波动特征及其可预测性研究

通过对沪、深股指高频数据的实证研究,验证了中国股票市场收益率分布的"尖峰胖尾"特征,发现了沪、深股票市场恢复正态分布假设(therecoveryofGaussiandistribution)的特征时间标度以及沪、深股市在交易日内的波动(intradayvolatility)特性,并对沪、深股指波动的可预测性进行了初步的探索。     

基于深度学习和股票论坛数据的股市波动率预测精度研究

本文利用深度学习和股吧发帖数增长率数据对沪深300指数波动率进行样本外预测,将预测结果与19种波动率预测模型作对比,并用MCS方法检验各模型的预测精度。研究发现:深度学习预测效果明显好于选取的其他对比模型。另外,股票论坛数据对提升波动率预测精度有所贡献,但贡献有限。本文为波动率预测提供了一种更精确和更稳健的实现方法,探索了股票论坛数据在波动率预测上的应用,并拓展了深度学习在金融领域的运用。     

股价信息含量与企业资本配置效率研究

股价信息含量代表证券市场的信息效率,其与资本配置效率之间具有密切的相关关系.以股价波动同步性作为股价信息含量的度量指标,在借鉴Richardson模型计量自由现金流、过度投资和投资不足的基础上,以2001年～2008年在沪深证券交易所上市的制造业公司为研究样本,从过度投资和投资不足的视角研究股价信息含量与企业资本配置效率之间的因果关系.实证结果表明,随着股价信息含量的提高,企业滥用自由现金流进行过度投资的行为能够得到有效的抑制,股价信息含量的提高还可以有效缓解企业的投资不足,证券市场信息效率的提高可以改善资本的配置效率,研究结论有助于更好地理解证券市场信息效率对资本配置效率促进作用的微观机理.     

基于社会网络的情绪扩散与股价波动风险研究

投资者情绪对股价波动风险的影响是行为金融学的重要观点,据此,本文基于股市投资者社会网络构建具有连续性和时效性的情绪扩散模型,通过量化情绪扩散对股市投资者交易决策的影响,明确投资者情绪扩散与股价波动风险之间的影响机制,进而分析股价波动风险的影响因素和控制策略。研究结果表明,投资者情绪扩散能够促进股价的波动,而具体影响程度由情绪扩散特征、投资者特征以及股市特征共同决定,并且机构投资者对于股价波动的影响具有双重特征,基于不同影响因素的研究结果为股价波动风险的防范提供了监管参考。进一步研究表明,基于全局信息的目标免疫方法能够有效控制股价波动风险,这对于维护股市稳定具有重要的意义。     

Educational Landscapes and Urban Development. Contextual and Spatial Interfaces and Linkages

In the broad sociopolitical discussion on education quality within the last decade, it has become apparent that education is gaining importance for urban development, as well as space and the urban context are important dimensions of education. This becomes particularly evident in concepts for local educational landscapes (Ger. Bildungslandschaften). The young field of research on educational landscapes is currently lacking empirical research from spatial and planning sciences. In the paper, the current state of scientific research on educational landscapes in Germany and Europe and first insights to contextual and spatial interfaces and linkages between education and urban development in general are presented.     

Inventory Models with Continuous and Poisson Demands and Discounted and Average Costs

We develop a new, unified approach to treating continuous‐time stochastic inventory problems with both the average and discounted cost criteria. The approach involves the development of an adjusted discounted cycle cost formula, which has an appealing intuitive interpretation. We show for the first time that an (s, S) policy is optimal in the case of demand having a compound Poisson component as well as a constant rate component. Our demand structure simultaneously generalizes the classical EOQ model and the inventory models with Poisson demand, and we indicate the reasons why this task has been a difficult one. We do not require the surplus cost function to be convex or quasi‐convex as has been assumed in the literature. Finally, we show that the optimal s is unique, but we do not know if optimal S is unique.     

E-governance and Corruption-developments and Issues in Ethiopia

This paper reports the results of a survey of 400 respondents in Ethiopia about factors generating corruption and the potential of e-Governance to mitigate corruption. It is suggested that e-Governance can help not only in weeding out corruption but also in the establishment of sounder government citizen relationships in Ethiopia. While e-Governance cannot cure all the structural factors that breed corruption in the society, strategic implementation of e-Governance can help improve the critical variable in combating corruption-government citizen relationships. It is argued that while e-Governance initiatives can make important contributions to improving public services they can best do so by helping improve overall relationships between governments and citizens.

The Challenge of Political and Economic Change in Poland and Central and Eastern Europe

This article discusses political and economic changes in Poland, Central and Eastern Europe emerging since the demise of the ‘closed system’ in 1989. The presentation explores the range of change, the method and the sequence of change. General lessons in economic transition as identified by Polish Finance Minister Lezak Balcerowicz are discussed. The challenges involved in macroeconomic stabilization, radical liberalization, currency convertibility, subsidy reduction and conversion of state-owned enterprises are reviewed. Despite their complexity, economic and political reforms proved necessary and inevitable. This revised version was published online in July 2006 with corrections to the Cover Date.     

Work and shopping overflow — Consequences and differentiation among selected psychological and demographic characteristics

Contemporary individuals are forced to deal with excessive stimulation, which causes an overload in the cognitive and emotional areas. The purpose of this paper is to investigate the possible factors differentiating the perceived level of work and shopping overflow experienced by individuals and consequences of these states. Two psychological variables: cognitive control and sensation seeking, are chosen as potential factors differentiating the perceived levels of overflow. We assume that individuals with high cognitive control and sensation seeking will report lower levels of both types of examined overflows. Experiencing low overflow levels may manifest in the search for additional stimuli, rather than in the desire to limit them. Two indexes of behavior connected to seeking extra stimulation are selected: one belonging to the area of consumer behavior (readiness to participate in the experience economy) and one belonging to vocational behavior (choosing a boundaryless career). The quantitative study is conducted on a sample of 297 management students who are currently employed. The research results support the relation between cognitive control and perceived level of work and shopping overflow. Individuals who can cognitively control the situation and the incoming stimuli report lower levels of overflow. No significant relationship between sensation seeking and the level of overflow is found. The demographic variables that influence the perceived overflow are age and salary for work overflow and age for shopping overflow. As far as consequences of overflow are concerned, a low level of shopping overflow is related to readiness to participate in the experience economy. However, there is no link between work overflow and preferred career pattern. The managerial implications for human resource management and marketing strategy design are discussed.     

Review and preview of productivity research and applications

During the last two decades, productivity research and applications have not been given adequate importance when trying to attain excellence in the management of manufacturing enterprises. Recent developments in managerial philosophies Total Quality Management and Business Process Re-engineering , manufacturing technologies Flexible Manufacturing Systems, Computer Integrated Manufacturing, etc. and Information Technology innovations have made the traditional productivity improvement techniques obsolete. This article presents a review consisting of analyses of literature on productivity and a survey of manufacturing enterprises. A five-step preview strategy on productivity is enumerated which provides a meaningful direction towards future productivity research and application. The article is concluded by briefly describing the current research that is being carried out based on the preview strategy evolved.     

Modeling Pathology Workload and Complexity to Manage Risks and Improve Patient Quality and Safety

Anatomic pathology (AP) laboratories provide critical diagnostic information that help determine patient treatments and outcomes, but the risks of AP operations and their impact on patient safety and quality of care remain poorly recognized and undermanaged. Hospital-based laboratories face an operational and risk management challenge because clinical work of unknown quantity and complexity arrives with little advance notice, which results in fluctuations in workload that can push operations beyond planned capacity, leading to diagnostic delays and potential errors. Modeling the dynamics of workload and complexity in AP offers the opportunity to better use available information to manage risks. We developed a stock-and-flow model of a typical AP laboratory operation and identified key exogenous inputs that drive AP work. To test the model, we generated training and validations data sets by combining data from the electronic medical records and laboratory information systems over multiple years. We demonstrate the implementation of 10-day AP work forecast generated on a daily basis, and show its performance in comparison with actual work. Although the model somewhat underpredicts work as currently implemented, it provides a framework for prospective management of resources to ensure quality during workload surges. Although full implementation requires additional model development, we show that AP workload largely depends on few and accessible clinical inputs. Recognizing that level loading of work in a hospital is not practical, predictive modeling of work can empower laboratories to triage, schedule, or mobilize resources more effectively and better manage risks that reduce the quality or timeliness of diagnostic information.     

Definitions and linkages between operational and strategic flexibilities

This paper aims at clarifying the concept of strategic flexibility, starting from that much more common of manufacturing flexibility (or operational one). After characterizing the dimensions of the latter, a classification of strategic flexibility is presented which distinguishes four categories. The measures of strategic flexibility are also investigated. Then two analogies are pointed out with the operational flexibility. The first, of the cause-effect type, is on two levels: at the business level, the operational flexibility estimates the variation of practices, while the strategic flexibility measures the effect obtained on performances; at the corporate level, the operational flexibility estimates the variation of competences, while the strategic flexibility evaluates the change in business. The second analogy, related to the classification variables, permits the main types of operational and strategic flexibilities to be placed in a single framework. So this study seeks to provide a framework—which has not been proposed in prior literature—for analyzing and evaluating the correlated concepts of operational and strategic flexibilities, to create a theoretical foundation for future research and empirical testing.     

Review and reappraisal of modelling and predicting mental workload in single- and multi-task environments

The concept of mental workload has long been recognized as an important factor in individual performance within complex systems. It is documented that either overload or underload may degrade performance, and further affect the efficiency of the whole system. Therefore, systems designers need some explicit models to predict the mental workload imposed on individuals by the system at an early design phase so that alternative system designs can be evaluated. In examining mental-workload literature, it is found that few predictive mental-workload models have considered factors specific to individuals. This research aims to develop a practical framework for predicting mental workload in both single- and multi-task environments considering such individual factors. In order to describe mental workload more precisely and more completely, a framework for mentalworkload definitions, which contains instantaneous workload, average workload, accumulated workload, peak workload and overall workload, is proposed. In order to model individual factors, two new variables, i.e. effective workload and ineffective workload, are introduced to model the taskgenerated workload and individual-generated workload. The extension of the model to multi-task environments is also discussed. The proposed conceptual models are domain-independent and could be used to guide the development of operational models for different specific tasks.     

Additive and Multiplicative Models and Multistage Carcinogenesis Theory

In light of the Armitage-Doll multistage carcinogenesis theory, this paper examines the assumption that an additive relative risk relationship is indicative of two carcinogens that affect the same stage in the cancer process. We present formulas to compute excess cancer risks for a variety of patterns for limited exposure durations to two carcinogens that affect the first and penultimate stages; and using an index of synergy proposed by Thomas (1982), we find a number of these patterns to produce additive, or nearly additive, relative risk relationships. The consistent feature of these patterns is that the two exposure periods are of short duration and occur close together.