求解证券组合最优权重的几何方法

本文通过建立无非负约束和有非负约束条件下证券组合的临界线方程,分别给出了求解允许卖空与限制卖空时证券组合投资最优权重的一种方法。这种方法既可求解给定收益下的证券组合投资最优权重,又可求解给定风险条件下的证券组合投资最优权重。     

不允许卖空的β值证券投资决策模型研究

本文利用证券市场模型和资本资产定价模型 ( CAPM)简化了不允许卖空的Markowitz的证券组合决策模型 ,导出了不允许卖空的 β值证券组合投资决策模型 ,并研究了该模型的解及其性质     

卖空的事前威慑、公司治理与企业融资行为——基于融资融券制度的准自然实验检验

本文从卖空的事前威慑角度出发,探讨了我国卖空机制的引入对企业融资行为及其决策的作用机理,并基于我国证券市场实施融资融券制度所带来的准自然实验研究机会,采用双重差分模型,检验了卖空机制的引入对我国上市公司新增外部融资以及财务杠杆的影响程度。本文发现,与不允许卖空的企业相比,允许卖空的企业其新增的外部权益融资、债务融资以及外部融资总额均显著减少了,且新增债务融资的减少程度要比新增外部权益融资的减少程度更大,并引起了财务杠杆的下降。这些结果在那些内部治理水平较差或正向盈余管理程度较高的企业中得到了进一步地体现。本文的研究结果表明,尽管我国卖空机制的引入时间不长且实际的卖空交易量也很小,但卖空机制作为一种来自外部的治理机制正在发挥着事前的威慑作用,并通过弥补内部治理水平的不足而规制着企业的融资行为。     

组合证券资产选择的模糊最优化模型和有效边界的研究

本文针对组合让券资产选择问题,提出了兼顾收佃与风险的模糊最优化模型,给出了最优证券组合的计算方法,并对允许卖空与允许地空情况下的有效边界进行了研究。     

基于计算实验的卖空交易对股票市场的影响研究

采用计算实验的方法研究卖空机制的引入对股票市场的影响。构建双向连续竞价的人工股票市场平台,设定投资者依据价值因素、价格趋势因素和噪声因素预估股票收益,建立市场卖空交易机制及投资者在禁止卖空和允许卖空情形下的交易模型,对引入卖空机制前后以及不同保证金要求下的股票价格、波动性和流动性进行研究。研究结果表明,卖空交易具有高卖空低买回的特点,从而在下跌的市场中提升股价,在上涨的市场中抑制股价,并有效地降低市场波动,提高市场流动性。随着保证金比例的减小,市场波动和买卖价差先减小后增加,而市场深度一直增加;通过对订单簿的研究发现,过低的保证金会加剧买卖订单的不平衡,甚至出现流动性“枯竭”,说明流动性先增加后减小;保证金比例的进一步减小会导致市场崩溃;过高的杠杆比率反而会对市场质量造成损害。     

股票卖空压力能否抑制高管的在职消费?--基于中国融资融券的自然实验证据

本文检验中国资本市场融资融券制度所施加的股票卖空压力对企业高管在职消费的影响。以2007-2014年中国上市公司财务数据为样本,基于自然实验框架的双重差分模型进行检验,结果发现,允许卖空的上市公司,其高管在职消费水平与不能卖空的上市公司相比显著降低;进一步的研究则发现,股票卖空压力是通过缓解信息不对称程度和减少委托代理问题来抑制高管的在职消费。本文实证结果说明股票卖空对高管在职消费来说是一种潜在的外部治理机制。     

求解不允许卖空证券组合前沿的区间搜索方法

综合分析了不允许卖空时证券组合前沿的构成和性质 ,在此基础上给出了求解不允许卖空时证券组合前沿的区间搜索方法 .应用该方法可以方便迅速地求出带有大型协方差矩阵的非负证券组合前沿及构成前沿的全部抛物的解析式 .对于大型证券组合优化问题的求解以及最优证券组合选择理论和方法的实用化具有重要的理论意义和实用价值     

机会约束下的含有资本结构因子和交易成本的均值-VaR投资组合模型

本文在均值-方差模型和机会约束模型的基础上,提出了在允许卖空时的一类机会约束下含有资本结构因子和交易成本的均值-VaR证券投资组合模型,以期望收益率与置信水平为导向,在假设收益率服从正态分布的条件下,建立了其数学模型,并讨论了最优解的存在性和唯一性,以及最优解的解析表达式。     

不允许卖空情况下均值-方差和均值-VaR投资组合比较研究

文章提出了不允许卖空情况的均值-方差和均值-VaR两种投资组合模型,并运用不等式组的旋转算法或结合序列二次规划法进行求解.最后,以一个具体例子验证了上述算法的有效性.计算结果还表明,不允许卖空情况下,均值-VaR投资组合有效前沿为均值-方差投资组合有效前沿的子集;置信度越低,投资者越倾向于收益率大而风险也大的投资组合.     

基金投资组合的事前与事后分析

根据2000年12月31日的沪、深证券市场的基金公告,利用Markowitz有效边界理论,在不允许卖空的市场条件下,对沪、深证券市场中的6个基金的主要股票投资决策分别进行了事前分析与事后分析,进而对基金主要股票投资组合决策的优劣及其在证券市场上的运行业绩进行了评价.     

A Sales Forecast Model for Short‐Life‐Cycle Products: New Releases at Blockbuster

We develop, in this article, a sales model for movie and game products at Blockbuster. The model assumes that there are three sales components: the first is from consumers who have already committed to purchasing (or renting) a product (e.g., based on promotion of, or exposure to, the product prior to its launch); the second comes from consumers who are potential buyers of the product; and the third comes from either a networking effect on closely tied (as in a social group) potential buyers from previous buyers (in the case of movie rental and all retail products) or re‐rents (in the case of game rental). In addition, we explicitly formulate into our model dynamic interactions between these sales components, both within and across sales periods. This important feature is motivated by realism, and it significantly contributes to the accuracy of our model. The model is thoroughly tested against sales data for rental and retail products from Blockbuster. Our empirical results show that the model offers excellent fit to actual sales activity. We also demonstrate that the model is capable of delivering reasonable sales forecasts based solely on environmental data (e.g., theatrical sales, studio, genre, MPAA ratings, etc.) and actual first‐period sales. Accurate sales forecasts can lead to significant cost savings. In particular, it can improve the retail operations at Blockbuster by determining appropriate order quantities of products, which is critical in effective inventory management (i.e., it can reduce the extent of over‐stocking and under‐stocking). While our model is developed specifically for product sales at Blockbuster, we believe that with context‐dependent modifications, our modeling approach could also provide a reasonable basis for the study of sales for other short‐Life‐Cycle products.     

卖空制度、流动性与信息不对称问题研究——香港市场的个案

应用香港市场的案例,研究了引入卖空制度后个股的交易活跃程度、流动性、波动性与信息不对称的变化,提出了噪声交易者假说,即引入卖空制度后重要的变化是噪声交易者会出于对更高亏损可能的担心而退出交易或变得谨慎.实证结果发现:引入卖空制度会带来交易活跃程度下降、流动性下降以及信息不对称水平升高.同时,通过对知情交易概率(PIN)...     

不允许卖空下证券投资组合的区间二次规划问题

本文基于经典的Markowitz均值-方差模型,针对市场上不允许卖空的情况,提出了证券投资组合的区间二次规划模型,通过应用区间数排序方法(区间序关系、区间可能度和区间可接受度),给出了两种证券投资组合的区间非线性优化的数学转化模型,从而将不确定性证券投资组合模型转化为确定性的证券投资组合二次规划模型进行求解,并对由本文给出的三种求解方法与传统方法进行了比较。     

卖空制度、流动性与信息不对称问题研究———香港市场的个案

应用香港市场的案例, 研究了引入卖空制度后个股的交易活跃程度、流动性、波动性与信息不对称的变化, 提出了噪声交易者假说, 即引入卖空制度后重要的变化是噪声交易者会出于对更高亏损可能的担心而退出交易或变得谨慎.实证结果发现:引入卖空制度会带来交易活跃程度下降、流动性下降以及信息不对称水平升高.同时, 通过对知情交易概率(PIN)的分析发现, 在引入卖空制度后, PIN值确实呈现出显著升高的趋势, 而使其升高的因素就是噪声交易者参与程度降低.噪声交易者假说较好地解释了上述现象.     

融合内容分析和关联分析的短生命周期体验品需求特征模式挖掘方法研究

挖掘特定产品的需求模式无法从整体掌握该类产品的市场特征；短生命周期体验品因缺乏历史销售数据，并且销售总量波动性极大，尤其需要从整体掌握销售总量与产品属性间关系的需求特征规律，但又难以挖掘，亟待提出适用于该类产品的需求特征模式挖掘方法。基于按销售总量分区后各区的需求特征的规律性，提出了一种按销售总量分区、以已有产品介绍集和销售总量为源信息、适用于新产品开发前使用、融合内容分析和关联分析的短生命周期体验品需求特征模式挖掘方法。该方法包括基于内容分析法的产品属性挖掘方法和基于关联分析的产品属性关系模式挖掘方法。前者可以得到较全面的产品属性；后者能够构建不同销售总量区间内产品集的属性关系模式，得到各区间的产品属性关系网，获得高销售总量区间具备，但中、低区间不具备的属性关系模式，从而获得需求特征模式。通过不断更新产品介绍集和销售总量并迭代挖掘，该方法能够动态挖掘需求特征模式。最后利用2013至2016年国产犯罪和爱情类电影数据验证了该方法的可行性，并得到了这两类电影的产品属性及近年的需求特征模式，可用于指导这两类电影的创作。     

Profit implications of estimation methods for the allocation of marketing resources

We deal with the question whether estimating heterogeneous multiplicative sales response models without carry over effects by either ordinary least squares or Gibbs sampling makes a difference if resources (like advertising budgets, sales budgets, sales force sizes, sales calls) have to be allocated to sales units (like sales districts, customer groups, individual costumers or prospects) in a profit maximizing way and only short time series are available. To this end we generate artificial series on sales and allocations by stochastic simulation. These series are used to estimate multiplicative models whose coefficients are either specific to individual sales units or follow a hierarchical Bayesian framework. Ordinary least squares and Gibbs sampling serve as appropriate estimation methods. Performance of the two estimation methods is measured by recovery of optimal profits which are computed on the basis of the known true parameter values. We start to determine optimal allocations based on the plug-in method which uses average coefficients to determine expected profits. Gibbs sampling always leads to profits nearer to the true optima. This advantage of Gibbs sampling is especially pronounced for combinations with high average elasticity, high variation of elasticity and high number of sales units. On the other hand, differences between Gibbs sampling and OLS become smaller the more observations are available. Optimization with expected profits taking parameter uncertainty (i.e., the distribution of parameters) into account leads to higher profits than the plug-in method, but relative increases turn out to be rather small.     

Verbot von Leerverkäufen in der Krise

During the recent financial and economic crisis political and corporate representatives demanded for stricter regulations of short sales to limit the risks of price manipulation and potential stock price crashes. In autumn 2008 regulators of most industrial countries decided to implement temporary short sale restrictions to prevent a further collapse of the capital market. While some countries restricted only naked short sales and increased their disclosure requirements, other markets like the USA and Great Britain implemented a full ban on short selling. The analysis of these two markets supports the hypothesis that temporary bans are unlikely to prevent or limit large price drops in the affected stocks. Instead the results suggest that the implemented emergency measures led to a temporary overvaluation of stock prices and to a deterioration of market efficiency. These results become even more prominent for stocks with high dispersion of investor opinion.     

考虑消费者退货的制造商入侵策略研究

在考虑消费者退货的情形下，通过构建包括一个制造商、一个零售商和消费者的二级供应链模型，研究了订货量决策以及制造商开通直销渠道的问题。分析提供退款保证和决策顺序对均衡结果以及制造商开通直销渠道的影响。研究发现：在单一渠道供应链中，提供退款保证提高销量，制造商和零售商利润以及消费者剩余；在不提供退款保证情形下，制造商利润和零售商利润都随零售满意度递增；在提供退款保证情形下，制造商利润和零售商利润都随零售满意度先递减后递增；当直销渠道的成本较高时，制造商将不开通直销渠道；提供退款保证有利于制造商开通直销渠道。在双渠道供应链中：在顺序决策情形下，直销量随零售满意度递增，然而在同时决策情形下，直销量却随零售满意度递减；提供退款保证虽然降低零售商利润但能够提高消费者剩余，零售商利润随直销成本递增，在提供退款保证情形下，制造商利润和总利润随直销成本先递减后递增；当零售满意度较高，且直销成本也较高时，提供退款保证使制造商和零售商“双输”，当零售满意度较高，但直销成本较低时，提供退款保证使制造商和零售商达到(win-lose)。     

产能有限的供应商主导的双渠道分销策略研究

在供应商产能有限的背景下,研究供应商的最优分配策略和双渠道分销的问题。根据期望利润最大化建立供应商渠道分配模型,依据纳什均衡确定供应商的最优定价、最优产能和最优分销策略。结果表明,在双渠道策略的情况下,供应商应该优先满足销售企业的销售量。若供应链的销售量恰好得到满足,供应商应该按最优产能生产。供应商的渠道选择与供应商产能、供应链各节点的盈利能力和生产成本有关。     

The Value of Weather Information for E‐Commerce Operations

To be efficient, logistics operations in e‐commerce require warehousing and transportation resources to be aligned with sales. Customer orders must be fulfilled with short lead times to ensure high customer satisfaction, and the costly under‐utilization of workers must be avoided. To approach this ideal, forecasting order quantities with high accuracy is essential. Many drivers of online sales, including seasonality, special promotions and public holidays, are well known, and they have been frequently incorporated into forecasting approaches. However, the impact of weather on e‐commerce operations has not been rigorously analyzed. In this study, we integrate weather data into the sales forecasting of the largest European online fashion retailer. We find that sunshine, temperature, and rain have a significant impact on daily sales, particularly in the summer, on weekends, and on days with extreme weather. Using weather forecasts, we have significantly improved sales forecast accuracy. We find that including weather data in the sales forecast model can lead to fewer sales forecast errors, reducing them by, on average, 8.6% to 12.2% and up to 50.6% on summer weekends. In turn, the improvement in sales forecast accuracy has a measurable impact on logistics and warehousing operations. We quantify the value of incorporating weather forecasts in the planning process for the order fulfillment center workforce and show how their incorporation can be leveraged to reduce costs and increase performance. With a perfect information planning scenario, excess costs can be reduced by 11.6% compared with the cost reduction attainable with a baseline model that ignores weather information in workforce planning.