Approximating Large Diversified Portfolios

This paper considers a financial market with asset price dynamics modeled by a system of lognormal stochastic differential equations. A one‐dimensional stochastic differential equation for the approximate evolution of a large diversified portfolio formed by these assets is derived. This identifies the asymptotic dynamics of the portfolio as being a lognormal diffusion. Consequentially an efficient way for computing probabilities, derivative prices, and other quantities for the portfolio are obtained. Additionally, the asymptotic strong and weak orders of convergence with respect to the number of assets in the portfolio are determined.     

Efficient Universal Portfolios for Past-Dependent Target Classes

We present a new universal portfolio algorithm that achieves almost the same level of wealth as could be achieved by knowing stock prices ahead of time. Specifically the algorithm tracks the best in hindsight wealth achievable within target classes of linearly parameterized portfolio sequences. The target classes considered are more general than the standard constant rebalanced portfolio class and permit portfolio sequences to exhibit a continuous form of dependence on past prices or other side information. A primary advantage of the algorithm is that it is easily computable in a polynomial number of steps by way of simple closed-form expressions. This provides an edge over other universal algorithms that require both an exponential number of computations and numerical approximation.     

Trading Portfolios Electronically – An Experimental Approach

This paper focuses on a simple axiom – investors prefer to hold diversified combinations of assets. Arguing that pooling vehicles like mutual funds offer approximate solutions, we propose a portfolio trading mechanism that allows individuals to trade diverse combinations of assets through a single order. Given the complexity of the market mechanism, we construct a prototype of this trading system and test it through a series of laboratory experiments with student subjects. We address the quality of the price discovery process, quality of allocations, and efficiency of the market mechanism. Results from a set of laboratory experiments indicate that the performance of such systems is sensitive to design aspects as well as relative experience of participants.     

Optimal Portfolios with Bounded Capital at Risk

We consider some continuous-time Markowitz type portfolio problems that consist of maximizing expected terminal wealth under the constraint of an upper bound for the capital at risk. In a Black–Scholes setting we obtain closed-form explicit solutions and compare their form and implications to those of the classical continuous-time mean-variance problem. We also consider more general price processes that allow for larger fluctuations in the returns.     

Selection of Socially Responsible Portfolios Using Hedonic Prices

This paper presents a novel framework for selecting socially responsible investment (SRI) portfolios. The Hedonic Price Method (HPM) is applied to obtain an evaluation of SRI criteria that is integrated into a multi-objective mathematical programming model. The HPM breaks away from the traditional view that goods are the direct object of utility; on the contrary, it assumes that utility is derived from the properties or characteristics of the goods themselves. As far as the investment decision is concerned, we assume that socially responsible investmentmutual funds (SRI funds) constitute heterogeneous goods. Our approach allows us to obtain a portfolio, the financial performance of which is similar to that which the investor would have reached if he or she had not taken into account social, ethical, and environmental considerations when making his or her investment decisions. This is achieved by designing a two-stage multi-objective mathematical programming procedure. In the first stage, we achieve the maximum level of financial satisfaction that the investor can receive. In the second stage, the portfolio with the best financial–social behavior is built. For the purpose of this second stage, the first stage portfolio is used as a benchmark for the financial performance of a socially responsible portfolio. To apply this methodology, we use portfolios composed of socially responsible and conventional mutual funds domiciled in Spain.     

A Credit Risk Model for Consumer Loan Portfolios

ABSTRACT

We propose a credit risk model for consumer loan portfolios in Brazil. Consumer profiles and the risk classification of credit operations are used to segment the portfolios. Credit loss distributions for each segment are selected and used in a Monte Carlo simulation process to generate the loss distribution of the portfolios. The dependence among the credit losses in the different segments of the portfolios is modeled through an elliptical copula function. Statistical tests are done and show that the proposed model is adequate to represent credit loss distributions in consumer credit in Brazil.

RESUMEN.Proponemos un modelo para los créditos de riesgo de la cartera de préstamos al consumidor en Brasil. Los perfiles del consumidor y la clasificación del riesgo de las operaciones crediticias se utilizan para segmentar la cartera. La distribución de las pérdidas de los créditos de cada segmento se seleccionan e utilizan en un proceso de simulación Monte Carlo, para generar la distribución de las pérdidas de la cartera. La dependencia entre la pérdida del crédito en los diferentes segmentos de la cartera se modela utilizando una función de cópula elíptica. Las pruebas estadísticas se realizan y muestran que el modelo propuesto es apropiado para representar la distribución de la pérdida de crédito en el ramo de los créditos a los consumidores en Brasil.

RESUMO.Propomos um modelo de crédito de risco para portfólios de empréstimos ao consumidor, no Brasil. O perfil dos comsumidores e a classificação de risco das operações de crédito são usados para segmentar o portfólio. As distribuições de perda de crédito para cada segmento são selecionadas e usadas num processo de simulação Monte Carlo, para gerar a distribuição da perda do portfólio. A dependência entre a perda do crédito nos diferentes segmentos do portfólio é determinada por uma função de cópula elítica. Testes estatísticos foram realizados e demonstram que o modelo proposto é adequado, para representar as distribuições de perda de crédito no crédito ao consumidor, no Brasil.     

The Implications of the Home Bias in Equity Portfolios

Although the diversification benefits of international investment are well documented, many large equity portfolios remain heavily concentrated in their domestic stock market. The reason for this is sometimes given as a desire to hedge domestic inflation by holding domestic equities. The evidence is, however, that equities do not hedge inflation in this way for the types of investment horizon relevant to most portfolios. An alternative explanation is that there are costs, such as taxes, which prevent investors taking full advantage of international diversification. The magnitude of these costs necessary to explain the level of "home bias" is above the level of observable costs, such as withholding taxes. The implications of these results are that international capital markets are segmented not only by costs and restrictions, but also by other informational imperfections. They also imply that international corporate investment and financing decisions depend on the location of the investing company.     

Efficient Computation of Hedging Portfolios for Options with Discontinuous Payoffs

We consider the problem of computing hedging portfolios for options that may have discontinuous payoffs, in the framework of diffusion models in which the number of factors may be larger than the number of Brownian motions driving the model. Extending the work of Fournié et al. (1999) , as well as Ma and Zhang (2000) , using integration by parts of Malliavin calculus, we find two representations of the hedging portfolio in terms of expected values of random variables that do not involve differentiating the payoff function. Once this has been accomplished, the hedging portfolio can be computed by simple Monte Carlo. We find the theoretical bound for the error of the two methods. We also perform numerical experiments in order to compare these methods to two existing methods, and find that no method is clearly superior to others.     

Equally Weighted Portfolios of Randomly Selected Stocks and the Individual Investor

The article contrasts 500 randomly formed equally weighted portfolios (1/N) to 221 actively managed stock funds, individual stocks, and the IBrX-50 index, representing indexed stock funds, considering transaction costs. The sample are the 50 stocks in IBrX-50 index in January 2007 throughout 60 months. Investors are likely to achieve greater returns and return-to-risk ratios with a randomly formed 1/N portfolio than with a stock fund, particularly those targeting retail investors, or one of the 50 stocks also randomly drawn. These portfolios would also outperform the IBrX-50. Robustness tests with variations in size and frequency of rebalancing do not change conclusions.     

Value Preserving Strategies and a General Framework for Local Approaches to Optimal Portfolios

We present some new general results on the existence and form of value preserving portfolio strategies in a general semimartingale setting. The concept of value preservation is derived via a mean-variance argument. It is also embedded into a framework for local approaches to the problem of portfolio optimization.     

机械刀具加工技术分析

现代高效刀具如何适应迅速发展的当今世界,使用户尽可能达到效率最高化、赢利最大化、质量最优化,需要不断在关键技术上进行改进及创新.调查显示,刀具材料、刀具涂层、刀具结构是进行高效刀具关键技术开发中关注的主要内容.     

现代资产组合理论的一个拓展:出口市场组合模型——关于我国出口市场多元化的理论思考

出口多元化战略实施十多年以来,我国出口市场仍较为集中。出口多元化战略包括两层含义:产品的多元化和市场的多元化。国内理论界关于多元化战略的研究主要集中在前者,关于后者的研究则比较罕见。本文试图借鉴现代资产组合理论的思想,运用相对方差来衡量风险,构造了出口市场组合模型,用于定量分析多元化战略中的“市场多元化”问题,为降低我国产品出口所面临的市场风险提供理论指导。     

Configuration and Development of Alliance Portfolios: A Comparison of Same-Sector and Cross-Sector Partnerships

This paper explores the intersection between three processes associated with globalisation. First, the rise of emerging economies like China, Brazil and India, the so-called ‘Rising Powers’, and their potential to define the contours of globalisation, global production arrangements and global governance in the twenty-first century. Second, the importance of corporate social responsibility (CSR) goals in the shaping of global trade rules and industrial practices. Third, the significance of small firm clusters as critical sites of industrial competitiveness. Some of the most significant examples of successful, innovative and internationally competitive small firm clusters from the developing world are located in the ‘Rising Powers’ and cluster promotion is a core element of national industrial policy in some of these countries. There is also evidence of engagement by clustered actors with corporate social responsibility goals around labour and environmental impacts. While these three processes have been separately studied there has been no attempt to explore their intersections. This paper addresses this gap through a comparative analysis of secondary data, and a detailed reading of the literature, on CSR and clusters in Brazil, China and India. It assesses the evidence on small firm clusters in the Rising Power economies and considers how these Rising Power clusters engage with CSR goals pertaining to labour, social and environmental standards. It argues for a greater focus on the formal and informal institutional context, termed the ‘social contract’, in explaining divergent experiences and practices observed across these countries. This raises important questions for future academic and policy research on clusters, CSR and the Rising Powers. The paper concludes by outlining a research agenda to explore the local and global consequences of the relationship between Rising Power clusters and international labour and environmental standards.     

Artificial intelligence and machine learning as business tools: A framework for diagnosing value destruction potential

Artificial intelligence (AI) and machine learning (ML) may save money and improve the efficiency of business processes, but these technologies can also destroy business value, sometimes with grave consequences. The inability to identify and manage that risk can lead some managers to delay the adoption of these technologies and thus prevent them from realizing their potential. This article proposes a new framework by which to map the components of an AI solution and to identify and manage the value-destruction potential of AI and ML for businesses. We show how the defining characteristics of AI and ML can threaten the integrity of the AI system’s inputs, processes, and outcomes. We then draw from the concepts of value-creation content and value-creation process to show how these risks may hinder value creation or even result in value destruction. Finally, we illustrate the application of our framework with an example of the deployment of an AI-powered chatbot in customer service, and we discuss how to remedy the problems that arise.     

除雪抻器--自主研发的冷风除雪车

2004年12月10日，北京三兴汽车厂总装车间红幅高挂，热烈欢迎长春飞机场领导和技术人员一行来厂参加我国首台冷风除雪车——三兴多功能机场道面清扫车下线仪式。     

Think before you eat: photographic food diaries as intervention tools to change dietary decision making and attitudes

This paper examines the use of photographic and written food diaries as interventions to raise awareness of and change dietary habits. Weinstein's precaution adoption theory and Guagnano, Stern and Dietz's Attitude Behaviour Context theory provide the theoretical basis to explain why nutrition knowledge does not result in healthy eating behaviour and why an intervention may be necessary to change attitudes and behaviours. A pilot study using written and photographic food diaries was conducted with 43 participants. Qualitative analysis of participant interviews revealed that photographic food diaries can alter attitudes and behaviours associated with food choices, and they are more likely to do so than written diaries because they serve as an intervention at the point when decisions regarding what to eat are being made.     

Continental differences in purchasing strategies and tools

This article focuses on the similarities and differences between the continental purchasing strategies and tools of companies in Western Europe and North America. The main question examined here is the strategic priorities and tools that European and North American buyers use (at the category level) for direct purchases and how they differ. The analysis is based on an empirical study of 224 companies from 10 countries. The results suggest that Europeans emphasise a reduction in prices and total cost of ownership as strategic objectives, while North Americans place greater emphasis on compliance with social and ethical guidelines. Both groups place surprisingly little emphasis on environmental objectives. In terms of tools, North American buyers have higher utilisation of electronic tools in purchasing and in communicating with suppliers, while European buyers appear to more extensively use purchasing tools associated with rating and auditing suppliers. Overall, it appears that a majority of purchases take place in home countries and close-by regions. Accordingly, we argue that practices adopted there offer interesting insights for international purchasing of the companies.     

测评客服质量的新方式

近些年来越来越多的酒店经营者开始强烈的意识到为每一位客人提供卓越服务的重要性。这也使得为客人量身打造的评价系统变得更为普及,如在线的或是通过一些社交媒体进行评论,客人们可以通过这些渠道发表自己的观点看法。这使经营者们认识到酒店所提供的服务以及其服务的水平变得更加透明化。     

A counterpoint assessment of Vancouver international airport as a gateway to North America

The essential issue here is does the trans-Pacific market need a hub at Vancouver, and if so, can Vancouver position itself to meet that need. Critical to arriving at an appropriate answer will be understanding the changing trans-Pacific market, the applicable regulatory environments, the airlines in the market, and the competing hub airports. Although Vancouver's location and its history place it in a favorable position, success is far from a foregone conclusion. © 1999 John Wiley & Sons, Inc.