Symmetry and order in the portfolio allocation problem

Summary. This research studies the role of multivariate distribution structures on random asset returns in determining the optimal allocation vector for an expected utility maximizer. All our conclusions pertain for the set of risk averters. By carefully disturbing symmetry in the distribution of the, possibly covarying, returns, we ascertain the ordinal structure of the optimized allocation vector. Rank order of allocations is also established when a permutation symmetric random vector is mapped into the returns vector through location and scale shifts. It is shown that increased dispersion in the vectors of location and scale parameters benefit, ex-ante, investors as does a decrease in the rank correlation coefficient between the location and scale parameter vectors. Revealed preference comparative static results are identified for the location and scale vectors of asset returns. For most issues addressed, we arrive at much stronger inferences when a safe asset is available. Received: August 8, 2000; revised version: January 8, 2001     

国有经济结构分析与调整对策

国有经济战略调整是中央提出的国有企业改革和发展的重要目标。在计划经济体制向市场经济体制的转轨过程中，国有经济的分布仍不够合理，国有企业在竞争领域仍然占有很大的比重，在经济结构的优化方面仍然存在着一些不容忽视的问题。因此，对这一问题的深入研究，具有重要意义。     

马克思如何实现对黑格尔辩证法的改造

马克思是如何实现对黑格尔辩证法的唯物主义改造的呢?马克思反复强调,黑格尔哲学是一种“头足倒置”的哲学,通过推敲黑格尔和马克思的辩证法思想,本文认为马克思实现对黑格尔辩证法的改造,至少经过了三个倒置:倒置了黑格尔辩证法辩证发展的主体;倒置了黑格尔辩证法辩证发展的中介;倒置了黑格尔辩证法辩证发展的理论结构。     

The division of labour and market structure

Most firms produce most of the time under conditions of substantial economies of scale. The division of labour, according to Adam Smith the mainspring of wealth, is intrinsically an economies of scale phenomenon. Market structure in most industries in characterized by a small number of suppliers and a larger number of customers. I explain this law of small numbers as the equilibrium of two forces: the deconcentration effect of imitation and the market spliting effect of further refinements in the division of labour by innovation. A deconcentrated market creates larger incentives for market splitting (product differentiation) by innovation than a concentrated market. But market splitting raises concentration in the market and it raises the number of different markets in the economy. Before the economies of scale of old products are fully exploited, new products are being offered which again are produced under conditions of economies of scale.     

相互制农业保险在我国的困境及适用性

相互制保险在农业保险领域有着明显的优势。然而,相互制保险管理制度上的缺陷及其与农业保险的矛盾制约着相互制农业保险的发展。目前,在我国合作意识不强、农村合作经济组织发育不健全的情况下,开展相互制农业保险还有一定困难。因此,要开展相互制农业保险,必须选择合适的范围和地区,并对相互制保险进行制度创新,为相互制农业保险提供财政补贴,建立再保险机制,加强引导,减少行政干预。     

开发利用农业剩余物资源是解决木材短缺的重要途径

从我国木材资源匮乏,木材供应缺口严重这一事实出发,阐述了开发利用农业剩余物资源的迫切性和农业剩余物资源开发利用的现状,提出了开发利用农业剩余物资源的建议。     

美、德农业社会化服务提供的启示

美国的农业社会化服务主要由三个部分组成：农业公共服务体系、集体农业服务体系和私人农业服务体系。公司＋农场、公司＋农户以及合作供销是美国农业社会化服务的三种形式。德国的农业社会化服务体系在于农业专业合作社组织的成功发展,尤其是健全的农村金融服务体系,由一个具有三级层次结构的分权型组织组成,通过立法和提供一些优惠政策,政府在服务体系中起了重要作用。我国农业社会化服务体系的组成和服务形式与美、德十分相似,在推动农村经济发展方面却有一定差异,美国和德国农业社会化服务的经验对中国农业社会化服务的发展具有重要启示。     

国内外关于农机需求的理论与实证研究综述

本文从理论和实证研究两个角度回顾了国内外关于农机需求研究的重点文献，归纳了宏观和微观农机需求研究的共同理论基础，探讨了国内外对农机需求研究的进展，最后指出：农机需求的微观研究是目前国内农机需求研究的空白领域和值得进一步研究的、具有理论创新意义的发展方向。