A Brief Survey of Modern Optimization for Statisticians

Modern computational statistics is turning more and more to high‐dimensional optimization to handle the deluge of big data. Once a model is formulated, its parameters can be estimated by optimization. Because model parsimony is important, models routinely include non‐differentiable penalty terms such as the lasso. This sober reality complicates minimization and maximization. Our broad survey stresses a few important principles in algorithm design. Rather than view these principles in isolation, it is more productive to mix and match them. A few well‐chosen examples illustrate this point. Algorithm derivation is also emphasized, and theory is downplayed, particularly the abstractions of the convex calculus. Thus, our survey should be useful and accessible to a broad audience.     

中国 R & D 强度区位分布条件因素的差异分析--基于稳健MM估计的EBA模型的实证研究

依据空间计量经济学的相关理论,运用稳健MM估计的EBA （异常值检验的极值边界分析）模型,采用中国30个省际区域2002～2012年的面板数据,实证研究中国东部、中部、西部地区R&D强度区位分布条件的“稳健性（Robust ）”影响因素。结果表明：我国东部、中部、西部各地区的R&D强度存在差异,且其影响因素也不尽相同。R&D强度较高的东部地区,科技水平、市场规模、固定资产投资、要素禀赋等4个因素对中国R&D强度具有抗干扰的“稳健性”影响;R&D强度中等的中部地区,3个“稳健性”影响因素是政府公共政策、科技水平和要素禀赋;而对于R&D强度较低的西部地区,技术创新和要素禀赋对提高R&D强度作用具有“稳健性”。由此揭示我国R&D强度的发展规律以及各区域间的差异性,并根据实证结论提出一些政策建议,为各地区制定科技政策目标和实施方案提供经验证据和决策参考。     

A worldwide analysis of trend in crop yields and yield variability: Evidence from FAO data

The trend in crop yields and yield variability affects food security and impact agricultural and food policies. Recent studies in this area have either focused only on one country or performed global analysis on a handful of crops. We provide the first worldwide analysis of trend and variability for 8088 country-crop yield series taken from the FAO database, employing a robust estimator to cope with the adverse statistical effects of outliers. More than half of the series display a slowdown in yield growth due to a closing of the gap between realised and attainable yields as well as to agricultural policies promoting more sustainable agricultural practices. Around one fourth of the series show also an increase in yield variability as a consequence of climate change and changes in farm management practices. Yield variability is highest in Eastern Europe, Central Asia and Middle East and North Africa, where food security may be threatened.     

Population ageing in healthcare – a minor issue? Evidence from Switzerland

Our study shows that population ageing is a relevant determinant of healthcare expenditure (HCE). This conclusion supports the popular, but recently strongly contested, view that the coming population ageing will threaten the fiscal sustainability of health systems. We contribute to this debate, first by estimating the determinants of Swiss HCE with outlier-robust dynamic regressions, and second, by projecting Swiss HCE based on the estimates produced and new population scenarios. Medical advances and GDP per capita also play a decisive role. Governments can mitigate HCE growth by improving the health status of the population and by stimulating cost-effective and productive medical advances.     

The Use of Prior Information in Very Robust Regression for Fraud Detection

Misinvoicing is a major tool in fraud including money laundering. We develop a method of detecting the patterns of outliers that indicate systematic mis‐pricing. As the data only become available year by year, we develop a combination of very robust regression and the use of ‘cleaned’ prior information from earlier years, which leads to early and sharp indication of potentially fraudulent activity that can be passed to legal agencies to institute prosecution. As an example, we use yearly imports of a specific seafood into the European Union. This is only one of over one million annual data sets, each of which can currently potentially contain 336 observations. We provide a solution to the resulting big data problem, which requires analysis with the minimum of human intervention.     

GOVERNMENT SIZE AND GROWTH: A SURVEY AND INTERPRETATION OF THE EVIDENCE – A COMMENT

In contrast to the commonly held view, Bergh and Henrekson (2011) conclude that a consensus has almost been reached on the thesis that government size is negatively correlated with economic growth in developed countries. They underpin this by claiming that the only study in the survey to deviate from this consensus view, i.e. Colombier (2009), was rebutted by Bergh and Öhrn (2011). This comment shows that the claim by Bergh and Henrekson (2011) cannot be upheld because the analysis by Bergh and Öhrn (2011) is based on a flawed dataset. The re‐estimation of Colombier's (2009) regressions with time‐fixed effect does not reject his main findings. Moreover, it is demonstrated that recent empirical evidence on the growth impact of government size in rich countries is not as unanimous as the survey by Bergh and Henrekson (2011) suggests. Thus, the claim that a consensus view has been reached is premature.     

The effect of reducing risk and improving personal motivation on the adoption of knowledge repository system

The role of Knowledge Repository Systems (KRSs) is to provide the exchanging intermediaries of explicit knowledge between knowledge contributors and knowledge seekers to assist knowledge sharing of employees in the organization. However, there is still a lack of deep understanding of how to reduce perceived risk and improve personal motivation on the adoption of KRSs in previous research. The paper presents social-psychological-technical perspectives to integrate social factors of reduced perceived risk (trust and organizational support) into Motivation Model (MM) and develop a comprehensive framework for assessing and analyzing the interaction of technology with the social, psychological, and behavioral aspects in KRSs. The proposed framework is validated with 528 respondents from teaching hospitals located in Taiwan, which shows that social factors of reduced perceived risk, personal motivation factors, and technology quality factors are three key factors affecting the acceptance of the KRSs. In other words, technological, social, psychological aspects will affect simultaneously behavioral intention in KRSs. Moreover, the psychological aspects are important mediators among technological, social, and behavioral aspects. The findings may be used as theoretical base for future research and offer empirical foresight to managers of organizations in assessing and evaluating the performance of the KRSs.     

浅谈西门子MM440变频器的安装与使用

西门子MM440变频器在许多工业领域得到应用,如何能够快速掌握其安装与使用方法,会更利于其发展和得到广大技术工作人员的拥护。本文就其组成、安装与使用三个方面进行初步交流。     

从公司资本结构理论新进展看我国上市公司融资政策取向

以MM定理为起点，研究了公司资本结构理论逐步引入公司所得税、破产风险、个人所得税、不完全信息的发展过程。分析了我国上市公司资本结构所处的经济现实条件与MM定理前提条件方面存在的差异，在此基础上，提出了优化我国上市公司资本结构的政策建议。     

西方企业资本结构理论评述

西方企业资本结构理论的研究方式大体上有三种体系:一是早期企业资本结构理论,但很不成熟;二是 现代企业资本结构理论,开创了资本结构理论研究和经济学研究充分融合的先例;再者是信息不对称理论,从企业内 部因素着手,重在研究制度设计,为企业资本结构理论研究开辟了新的研究方向。