An algebraic theory of portfolio allocation

Summary. Using group and majorization theory, we explore what can be established about allocation of funds among assets when asymmetries in the returns vector are carefully controlled. The key insight is that preferences over allocations can be partially ordered via majorized convex hulls that have been generated by a permutation group. Group transitivity suffices to ensure complete portfolio diversification. Point-wise stabilizer subgroups admit sectoral separability in fund allocations. We also bound the admissible allocation vector by a set of linear constraints the coefficients of which are determined by group operations on location and scale asymmetries in the rate of returns vector. For a distribution that is symmetric under a reflection group, the linear constraints may be further strengthened whenever there exists an hyperplane that separates convex sets. Received: May 15, 2001; revised version: March 20, 2002 RID="*" ID="*" Journal paper No. J-19797 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 3463, and supported by Hatch Act and State of Iowa funds. Correspondence to: D. A. Hennessy     

换工作对收入水平和收入增长的影响

本文利用中国社会科学院2002年的CHIPS数据,分析了换工作对于劳动者收入水平和收入增长的影响。本文通过控制初始的收入水平来解决异质性的影响。结果表明,对于初始收入水平较低的样本,换工作对其收入有正的影响,而对于初始收入较高的样本,换工作则有负的影响。如果直接考察换工作对于收入增长的影响,给定初始收入和其他特征,换工作对于收入增长的平均影响是正的。不仅如此,换工作对于低收入者的收入增长有较大的正的影响。     

农业产业化龙头企业经营风险防控——基于三鹿集团个案分析

作为我国乳业巨头的三鹿集团宣布破产,可谓食品界的大地震。反思三鹿毒奶粉事件我们不难发现,造成三鹿悲剧的,三聚氰胺只是个导火索,而事件背后的经营风险管理失控才是真正的罪魁祸首。本文通过对三鹿经营风险因素的剖析,为我国农业产业化龙头企业风险控制提出建议。     

Notes on some present day Questions regarding Mortality

Abstract

In the absence of any definite development of actuarial science in Great Britain which would be a suitable subject for this paper I considered that the most useful course would be to discuss some of the problems which are at present exercising my own mind, and no doubt the minds of many of my colleagues. Probably, many of these questions are akin to others which arise in other countries, so that their discussion at a meeting such as this may prove of mutual interest, while even if they are peculiar to ourselves, a disclosure of our doubts and difficulties will indicate the directions in which future developments may be expected. I must, however, emphasize that any views expressed are purely personal, and do not in any way pretend to represent a consensus of British actuarial opinion. Throughout this paper only Ordinary (as opposed to Industrial) business in considered.     

丁家屋子地区孔店组高凝油增产措施选层技术

文章通过对丁家屋子地区孔店组高凝油测试资料进行分析,将储层分为四类,并对每类储层的试油工艺及效果进行了分析,找到了增产措施选层原则。     

Where has all the skewness gone? The decline in high-growth (young) firms in the U.S.

The pace of business dynamism and entrepreneurship in the U.S. has declined over recent decades. We show that the character of that decline changed around 2000. Since 2000 the decline in dynamism and entrepreneurship has been accompanied by a decline in high-growth young firms. Prior research has shown that the sustained contribution of business startups to job creation stems from a relatively small fraction of high-growth young firms. The presence of these high-growth young firms contributes to a highly (positively) skewed firm growth rate distribution. In 1999, a firm at the 90th percentile of the employment growth rate distribution grew about 31 percent faster than the median firm. Moreover, the 90−50 differential was 16 percent larger than the 50−10 differential reflecting the positive skewness of the employment growth rate distribution. We show that the shape of the firm employment growth distribution changes substantially in the post-2000 period. By 2007, the 90−50 differential was only 4 percent larger than the 50−10, and it continued to exhibit a trend decline through 2011. The overall decline reflects a sharp drop in the 90th percentile of the growth rate distribution accounted for by the declining share of young firms and the declining propensity for young firms to be high-growth firms.     

经济增长模型中的储蓄率内生化问题

本文讨论经济增长模型中储蓄率内生化的各种问题,包括有限寿命与无限寿命、确定寿命与不确定寿命、不确定寿命下的消费决策方法、不确定寿命下非预料死亡者的遗产如何处理、个人生命如何分期、个人如何预期未来收入等。强调了寿命假定与人口年龄结构的内在联系,提出了寿命不确定下个人消费决策的新方法,探讨了有关未来收入的趋势预期和水平预期,并分析了哪一种更接近实际。     

Is group selection necessary? An alternative interpretation of homogeneous Middleman groups: Comments on Janet Landa’s paper

This article critiques the efforts by Janet Landa, David Sloan Wilson and others to use group selection paradigms to explain the success of homogenous middlemen groups (HMGs). It argues that group selection theory cannot explain the conflicts of interests that arise within HMGs or why they dissolve in certain occasions. Landa’s earlier explanations, which stressed the combination of genetic (kinship) and social bonds in the creation of trust and cooperation in the extension of credit and the creation of local public goods, better predicts both the strength and weaknesses of HMGs.