Stable Asymptotics for M‐estimators

We review some first‐order and higher‐order asymptotic techniques for M‐estimators, and we study their stability in the presence of data contaminations. We show that the estimating function (ψ) and its derivative with respect to the parameter play a central role. We discuss in detail the first‐order Gaussian density approximation, saddlepoint density approximation, saddlepoint test, tail area approximation via the Lugannani–Rice formula and empirical saddlepoint density approximation (a technique related to the empirical likelihood method). For all these asymptotics, we show that a bounded ψ (in the Euclidean norm) and a bounded (e.g. in the Frobenius norm) yield stable inference in the presence of data contamination. We motivate and illustrate our findings by theoretical and numerical examples about the benchmark case of one‐dimensional location model.     

The role of transaction costs and risk aversion when selecting between one and two regimes for portfolio models

Estimation of the inputs is the main problem when applying portfolio analysis, and Markov regime-switching models have been shown to improve these estimates. We investigate whether the use of two-regime models remains superior across a range of values of risk aversion and transaction costs, in the presence of skewness and kurtosis and no short sales. Our results for US data suggest that, due to differences in their risk preferences and transactions costs, most retail investors may prefer to use one-regime models, while investment banks may prefer to use two-regime models.     

A note on the dynamics of learning alliances: competition,cooperation, and relative scope

Khanna, Gulati, and Nohria (1998) examine the dynamics of alliance learning and develop a conceptual framework designed to capture the tension between cooperation and competition. Based on the concepts of private and common benefits and relative scope, the authors explore firms' learning behavior patterns. This note comments on the framework and suggests that although the framework introduces some interesting concepts, the reliance on simple models from economic theory leaves the framework somewhat disconnected from the process of alliance management. Copyright © 2000 John Wiley & Sons, Ltd.     

一种用于隧道覆盖的超宽带单极子天线

通过分析目前隧道或地铁工程中经常使用的泄漏电缆覆盖成本较高的不足,提出了 一种新的设计方案——双向天线覆盖,并且根据平面单极子的辐射特性,采用电磁仿真软件 Ansoft HFSS建模仿真,设计并实现了一款在155～1057 GHz频带内具有良好阻抗特 性的环形椭圆平面单极子天线,其相对带宽接近150%,水平面辐射方向图是沿着隧道双向分 布的,而且实测结果与仿真数据相吻合。该天线结构简单,容易实现,采用壁挂形式,安装 方式简单可靠,造价成本低。     

Reconsidering the Relationship between Inflation and Relative Price Variability

It has long been popularly believed that the relationship between inflation and relative price variability (RPV) is positive and stable. Using disaggregated CPI data for the United States and Japan, however, this study finds that the relationship is neither linear nor stable over time. The overall relationship is approximately U‐shaped around a nonzero threshold inflation rate. RPV therefore changes not with the inflation rate per se, but with the deviation of inflation from the threshold inflation rate. More importantly, the relationship is by no means stable over time but instead varies significantly in a way that coincides with regime changes of inflation or monetary policy. The relationship was positive during the period of high inflation of the 1970s and the early 1980s, as has been documented by a number of previous studies, whereas it takes a U‐shape profile during the Great Moderation. The results are robust to the use of core inflation, which excludes the traditionally volatile prices of food and energy. This paper then presents a modified version of the Calvo‐type sticky price model to describe the observed empirical regularities. Simulation experiments show that the modified Calvo model fits the data well, and that the underlying relationship hinges upon the degree of price rigidity, which is systematically related to inflation regime. For countries and periods with low inflation rates, the relationship takes a U‐shape as price adjustment is more sticky. In a high‐inflation environment, when price setting becomes more flexible, the U‐shaped profile vanishes.     

从相对承载力视角看湖北省水资源可持续利用

采用相对资源承载力的研究思路与方法,研究了湖北省2000～2007年相对水资源承载力、相对经济资源承载力和综合承载力的情况及其变化过程。结果表明:与全国平均水平相比,湖北省相对资源承载力处于超载状态;与中部其他5省相比,除湖南省外,湖北省相对资源承载力处于富余状态;湖北省的水资源对综合承载力的贡献率高于经济资源对综合承载力的贡献率,是湖北省人口的主要承载资源;与湖北省的平均水平相比,湖北省17市(州)相对资源承载力的地区差异较为明显。建议采取综合措施,促进湖北省水资源的可持续利用。     

二元结构环境下的IPO定价模型研究

本文传承我国国情和股票发行定价制度的历史、现状,基于相对估价法的基本原理,采用"变异系数法"分析企业特质,辅之以相关性的技术处理,构建了一个企业特质评价指标体系,采用"标准化加权评价法"加以评价后,创造性地通过"标准差倍数法"的技术处理将之纳入定价模型.然后分别立足于一级市场和二级市场,构建一步静态模型和两步静态模型,为检验模型的应用效果,本文提出了IPO定价的四个检验标准,并做了实证检验评估.最后结合新股循价制度改革和实践,对IPO定价问题做进一步的检验探讨.     

资本品进口、资本技能互补与中国的相对工资差距

中国是资本品净进口国,资本品进口引致资本积累并通过资本与技能互补效应增加对熟练劳动力的相对需求,是影响熟练劳动力与非熟练劳动力之间相对工资差距的一个重要机制。文章实证检验了资本品进口与中国熟练劳动力的互补效应及其对中国相对工资差距的影响。研究结论表明：资本与技能互补效应在中国长期存在,资本品进口促进了中国的资本积累,并通过资本与技能互补效应提高了熟练劳动力的边际产出,增加了对熟练劳动力的相对需求,扩大了相对工资差距。然而,劳动力的相对数量效应和相对效率效应对中国不断扩大的相对工资差距的解释力不强。     

中美制造业双边贸易对美国相对工资差距的影响研究*

在新古典贸易理论一般均衡的框架之下,运用1997-2014年中美两国的投入产出、贸易和工资数据,本文定量考察了中美制造业产品的双边贸易同美国制造业相对工资差距的关系。结果发现,美国从中国的净进口对美国制造业非熟练劳动力和熟练劳动力相对工资差距扩大存在影响,但影响幅度较小,贸易并不是引起相对收入差距扩大的唯一原因。但随着中美双边制造业贸易的进一步发展,美中贸易对美国工资差距的影响可能越来越大,以保护非熟练劳动力为名对中国产品实施贸易限制的呼声将会更高。