Migration decisions under ambiguity: Migration distance effects revisited

There is ample evidence that distance has a strong negative effect on migration. Despite its significance in migration decisions, scholars rarely explore the migration distance effect deeper than the first level of interpretation derived from the simple neoclassical theory of migration. This study revisits the migration distance effect in the spirit of Knightian distinction between risk and uncertainty. To this end, this study attempts to construct estimates of the risk premium migrants are willing to pay to avoid the risk associated with migration distance. The results show that the magnitude of the distance effect is not rationalized by risk aversion in the Arrow–Pratt sense (Arrow, 1965, The theory of risk aversion, Yrjo Jahnssonin Saatio, Helsinki, Finland, 90; Pratt, 1964, Econometrica, 32, 122). In particular, the risk premium demanded by distant rural residents is unjustifiably higher compared with that of those living closer to urban areas in their migration decisions. The results suggest that the migration distance effect is analogous to the equity home bias puzzle and the Ellsberg paradox in that the assumption of subjective expected utility can lead to seemingly irrational human behaviors. Some of the findings in this study shed light on the role of subjective aspects such as perception, confidence, and pessimism in migration decisions, which have been neglected in the literature.     

OPTIONS AND EFFICIENCY IN MULTIDATE SECURITY MARKETS

This paper extends the work of Ross (1976; Q. J. Econ. (90)1, 75–89) to multidate security markets. First, we show that if a primitive security separates states at the terminal date, then there exist multiperiod European options on that security generating dynamically complete markets. Second, we show that if a primitive security conditionally separates states at the terminal date, then there exist multiperiod European options on that security generating generically dynamically complete markets provided that certain conditions hold. Third, we show that there are economies for which the minimum number of multiperiod European options on a primitive security generating generically dynamically complete markets is relatively large. Finally, we show that in these economies, a relatively small number of multiperiod European options on possibly different portfolio strategies of primitive securities generates generically dynamically complete markets.     

中国城市化有关问题初探

城市化问题是当代社会经济发展的重大问题，是涉及到自然资源的合理开发利用，农村人口转化、剩余劳动力的走向以及城市工业、第三产业发展的关键问题。     

城镇化水平与农民收入的相关性研究

城镇化水平与农民人均收入存在着密切关系，即城镇化水平越高，农民人均收入越高；城镇化水平越低，农民人均收入越低。因此，要增加农民人均收入，就必须提高城镇化水平，特别是提高中西部省份的城镇化水平。文章主要运用统计学中的回归分析方法来阐述这一观点。     

Boundedly complete families which are not complete

Summary Completeness of a family of probability distributions implies its bounded completeness but not conversely. An example of a family which is boundedly complete but not complete was presented by Lehmann and Scheffe [5]. This appears to be the only such example quoted in the statistical literature. The purpose of this note is to provide further examples of this type. It is shown that any given family of power series distributions can be used to construct a class containing infinitely many boundedly complete, but not complete, families. Furthermore, it is shown that the family of continuous distributions , is boundedly complete, but not complete, whereU denotes the uniform distribution on [a, b] and {P _ϑ,ϑ ∈ IR}, is a translation family generated by a distributionP ₀ with mean value zero, which is continuous with respect to the Lebesgue measure.     

美国的城市化进程与现代城市规划联系的解读

回顾了美国城市化的独特发展历程和美国现代城市规划历史,并就二者之间的相互关系进行了探讨,以期对处于转型期的中国城市化发展有所启示和借鉴.     

城市化进程中的产业政策选择

当前我国已进入城市化加速阶段,促进城市化水平的提高应成为制定产业政策的重要出发点.从各产业的比较劳动生产率、国际竞争力和就业吸纳能力等方面入手进行分析,筛选出了若干发展潜力大、就业吸纳能力强的行业;并指出这些行业在我国未来的城市化进程中将起到至关重要的作用,应制定相应的政策加以重点扶持.     

我国城市化危及土地资源持续利用的立法原因探析

随着我国城市化进程的不断加快 ,土地资源供给的有限性与人们对土地资源需求的无限性之间的矛盾日益突显。而在此背景下重新修订公布的《土地管理法》在涉及建设用地需求的无限扩展与农业用地数量的持续下降这两个突出问题上 ,并没有明确政府的职能定位 ,也反映出了相关制度的模糊性。本文就此进行了探讨。     

城市郊区化模式比较与我国的选择——以英美澳日等国为例

英美澳日四个发达国家分布在文化背景不同的四个大陆,其城市化进程的模式不完全相同,尤其是后城市化阶段表现出的特点更加鲜明.对比分析发现,四个国家的城市化进程中在政府政策、城乡关系、不同规模的城市所起的作用等诸多方面存在着差别,英澳日等国的政府在投资、规划以及法律建设等方面的介入发挥着重要作用,而美国则是市场机制起主导作用的城市化模式.发达国家取得的这些经验对于我国的城市发展有非常重要的借鉴意义.     

煤炭资源型城市聚集经济与城市化水平研究

运用可变权系数综合评价模型对2002年中国煤炭资源型城市城市化水平进行测度;基于1999～2002年度煤炭城市面板数据,应用随机效应模型估计煤炭城市聚集经济水平;结果表明,我国煤炭城市城市空间经济结构效率和其城市化水平并不具有正相关性,许多城市化水平相对较高的煤炭城市的聚集经济较差,并没有显示出城市化经济的优势.