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.     

大兴安岭林业持续发展的探讨

大兴安岭森林是受冻土控制下形成和发展的，保存了大量淡水资源，形成了冷湿生态环境。大兴安岭林业持续发展必须按特殊方式经营，建立生态林业，从而发挥其固有的多种效益。     

天保工程建设：中央与地方政府投资博弈

通过构建我国中央与地方林业投资的博弈模型,深入分析了两类利益主体所处的数种纳什均衡,借以探讨了在天然林保护工程实施中地方林业配套资金难以落实的问题,并查找原因,提出建议。     

领导干部在农业结构调整中应强化十种意识

新阶段的农业结构调整,必须适应变化了的新形势.为此,要进一步深化对农业结构调整的认识,牢固树立大农业意识、市场意识、规则意识、品牌意识、科技意识、信息意识、产业意识、工业意识、城镇意识和服务意识.     

Stability and Segregation in Group Formation

This paper presents a model of group formation based on the assumption that individuals prefer to associate with people similar to them. It is shown that, in general, if the number of groups that can be formed is bounded, then a stable partition of the society into groups may not exist. (A partition is defined as stable if none of the individuals would prefer be in a different group than the one he is in.) However, if individuals' characteristics are one-dimensional, then a stable partition always exists. We give sufficient conditions for stable partitions to be segregating (in the sense that, for example, low-characteristic individuals are in one group and high-characteristic ones are in another) and Pareto efficient. In addition, we propose a dynamic model of individual myopic behavior describing the evolution of group formation to an eventual stable, segregating, and Pareto efficient partition. Journal of Economic Literature Classification Numbers: C72, H41.