On the emergence of scale-free production networks

We propose a simple dynamical model for the formation of production networks among monopolistically competitive firms. The model subsumes the standard general equilibrium approach à la Arrow–Debreu but displays a wide set of potential dynamic behaviors. It robustly reproduces key stylized facts of firms׳ demographics. Our main result is that competition between intermediate good producers generically leads to the emergence of scale-free production networks.     

住宅套型的物理性能质量衡定标准探讨

本文从住宅套型的声环境、光环境、热舒适环境和通风环境四大方面入手,对影响住宅套型性能质量之物理性能质量进行探讨。     

The extent of nonstationarity of beta

This paper investigates the extent of nonstationarity of beta across the firm size and the beta magnitude by suggesting the sequential parameter stationarity model and estimating change-points of betas. The high-beta firm has shorter stationary interval, which means that its beta changes more frequently than do the low-beta firm's. The firm size, however, does not have a monotonic relation with the length of stationary interval. The small and large firms have relatively shorter stationary interval than do the mid-sized firms. The average length of stationary interval is estimated about five years (exactly 54.19 months). This fact could support the currently widely-used arbitrary 5-year assumption of beta stationarity. The fluctuation of the large firm's beta is more severe than the small firm's, and the high- and low-beta firms have the relatively greater fluctuating betas than do the mid-beta firms. The frequency of detected change-points is found to be positively related to market returns. When the market return is high, the systematic risk changes more frequently, and vice versa.     

Portfolio Returns,Market Volatility,and Seasonality

This paper examines three important issues related to the relationship between stock returns and volatility. First, are Duffee's (1995) findings of the relationship between individual stock returns and volatility valid at the portfolio level? Second, is there a seasonality of the market return volatility? Lastly, do size portfolio returns react symmetrically to the market volatility during business cycles? We find that the market volatility exhibits strong autocorrelation and small size portfolio returns exhibit seasonality. However, this phenomenon is not present in large size portfolios. For the entire sample period of 1962–1995, the highest average monthly volatility occurred in October, followed by November, and then January. Examining the two sub-sample periods, we find that the average market volatility increases by 15.4% in the second sample period of 1980–1995 compared to the first sample period of 1962–1979. During the contraction period, the average market volatility is 60.9% higher than that during the expansion period. Using a binary regression model, we find that size portfolio returns react asymmetrically with the market volatility during business cycles. This paper documents a strongly negative contemporaneous relationship between the size portfolio returns and the market volatility that is consistent with the previous findings at the aggregate level, but is inconsistent with the findings at the individual firm level. In contrast with the previous findings, however, we find an ambiguous relationship between the percentage change in the market volatility and the contemporaneous stock portfolio returns. This ambiguity is attributed to strongly negative contemporaneous and one-month ahead relationships between the market volatility and portfolio returns.

     

用分组垫片法解装配尺寸链的研究

本文系统研究了用分组垫片法解装配尺寸链时的计算方法。提出了改进和完善用分组垫片法解装配尺寸链的四个问题:组成环经济公差的标准化;理论计算垫片分组数的取整;每组垫片的分配数量和装配尺寸链的概率计算法。并给出了相应的分析和计算方法,使其理论能够更准确、更方便地运用于实际设计过程中。     

Gross national accumulation

Low birth rates, longevity, family disintegration, and other factors have reduced the size of the average household. At the same time household size is shrinking, new housing offers twice the floor space per occupant of old housing. Small households are inefficient users of space, utilities, furniture, and equipment. As these factors converge, the result is over consumption of durables and vast stockpiles of possessions just awaiting disposal when the baby boom generation passes on. The rightful heirs to these possessions are themselves accumulators, and will most likely have little use for what is left to them. What does the future hold for consumption, savings, and demand for housing? Booming flea markets, bigger homes as warehouses, a decline in consumption, or an epidemic of display and collection? Public policies have limited leverage on private behavior.     

我国开放式基金规模确定模型初探

通过对美国共同基金关于基金规模的数学模型分析,我们发现基金规模与基金经理人能力和流动性赎回密不可分。从美国的有关模型分析与优秀经验来谈我国为确定基金规模所采取的措施:首先讨论了保证基金管理人发挥其能力的一些政策性建议,其次讨论了减少流动性赎回所采取的措施。     

Unobserved firm heterogeneity and the size-exports nexus: Evidence from German panel data

This paper starts from the stylized fact that firm size and exporting tends to be positively related. Using large sets of establishment panel data for three different industries from official statistics, evidence is presented that the familiar picture of an export/sales ratio that increases (at a decreasing rate) with firm size vanishes if unobserved firm heterogeneity is controlled for in a fixed-effects fractional logit regression model. This finding is well in line with the fact that many small firms are “hidden export champions.” JEL no. F10, D21, L60     

中国商业银行信息技术资本的边际生产率及最优规模

基于12家商业银行1997～2005年间的数据，对商业银行信息技术资本的边际生产率和最优投入规模的实证研究结果表明，我国商业银行信息技术资本的边际生产率是正的，且其大小受银行规模和时间的影响；四大商业银行信息技术资本的边际生产率小于中小规模商业银行；银行整体的信息技术资本边际生产率随时间呈现不断增长的趋势；四大商业银行信息技术投资已经超过了最优规模，而中小商业银行尚未达到最优规模。四大商业银行应该着重提高信息技术资本的利用率，完善互补机制，而中小商业银行应进一步加大信息技术的投资量。研究结果证明，当前“信息技术生产率悖论”在我国商业银行中并不成立。     

中国金融业资产的规模与效率

通过在金融资产结构与经济增长模型中引入能够综合反映制度变迁的制度变量,证明国家制度变迁对一国金融资产结构与经济增长会起到促进或制约的作用.当制度供给与金融资产结构和经济增长对制度的需求达到均衡时,国家制度安排会优化金融资产结构、促进经济增长,否则便会出现规模与效率的"反比"现象,从而回答了我国金融资产规模与效率之间为什么出现悖论的问题.我国应积极发展非银行金融机构,实现金融体系多元化,对内开放,满足我国经济对多层次、多样化金融的需求,完善金融市场准入制度,优化市场参与主体结构,促进股票市场和银行协调发展.