交易成本的空间异质性与城市体系形成演化机理研究

城市从本质意义上理解是集聚化交易的空间秩序或制度,城市体系的形成受到城市间制度竞争的影响.作为制度分析的重要概念,本文引入交易成本来分析城市的体系演化,并以“长三角”城市体系为例进行了实证分析.文章认为,城市体系的形成是制度竞争和生产力进步的结果,很大程度在交易成本的空间异质性与运输成本之间交互作用中得到反映.受此影响,城市体系一般经历离散发展阶段、城市体系发展期和城市体系成熟期,并且随着交易成本空间异质性的深度演化,城市体系也将经历从“低水平均衡—不均衡—高水平均衡”的周期性的反复演变.     

子女离婚对老年人健康的影响研究--基于CLASS数据的实证分析

婚姻稳定性下降、人口老龄化加剧预示着越来越多的老年人会经历子女离婚,然而子女离婚是否以及如何影响老年父母健康尚缺乏研究。本文基于生命历程理论和社会性别理论,从老年健康的角度出发,强调来自家庭层面子女离婚的影响,并从家庭代际经济支持等方面分析子女离婚如何影响老年健康及其发生的机制,探索家庭内部影响因素间的作用与联系。本文利用2014年和2018年“中国老年社会追踪调查数据”(CLASS)分析子女离婚对老年父母健康状况的影响。研究发现对于当前我国老年人而言,子女离婚仍是少数,但子女离婚会对老年父母健康带来冲击,表现为有离婚子女的老年人更可能自评身体不健康、慢性病患病数量显著更多、精神健康水平更低;子女离婚对老年父母的健康负面影响具有持久性;相较于儿子离婚,女儿离婚的老年人更可能自觉身体不健康;子女离婚对父母健康的影响具有性别异质性,离婚更易影响女儿对父母的经济支持水平是一个重要原因。     

Heterogeneity in returns to college education: selection bias in contemporary taiwan

The causal impact of higher education on earnings may be heterogeneous across different members of a population. Using a newly developed instrumental-variable method in economics, we illustrate heterogeneous treatment effects of higher education on earnings resulting from sorting mechanisms that select individuals with certain unobserved attributes into college education. The setting of our empirical work is contemporary Taiwan - a transitional economy that has recently experienced a rapid expansion in higher education. We find distinct patterns by gender, with selection bias most clearly shown among women but not among men: the college return to earnings is on average greater for women who actually attended college than women who did not attend college.     

Parasitoid-mediated effects: apparent competition and the persistence of host–parasitoid assemblages

Indirect effects such as apparent competition (in which two hosts that do not compete for resources interact via a shared natural enemy) are increasingly being shown to be prevalent in the structure and function of ecological assemblages. Here, we review the empirical and theoretical evidence for these enemy-mediated effects in host–parasitoid assemblages. We first address questions about the design of experiments to test for apparent competition. Second, we consider factors likely to affect the coexistence of host species that share a parasitoid and are involved in apparent competition. We show that parasitoid aggregation, and the switching effect that this can generate when hosts occur in separate patches, not only promotes persistence but is also strongly stabilizing. The broader consequences of these effects are discussed. Received: November 6, 1998 / Accepted: January 13, 1999     

Regression-based estimation of the false negative fraction when multiple negatives are unverified

Summary.  The paper describes a method of estimating the false negative fraction of a multiple-screening test when individuals who test negatively on all K tests do not have their true disease status verified. The method proposed makes no explicit assumptions about the underlying heterogeneity of the population or about serial correlation of test results within an individual. Rather, it is based on estimating false negative fractions conditionally on observed diagnostic histories and extrapolating the observed patterns in these empirical frequencies by using logistic regression. The method is illustrated on, and motivated by, data on a multiple-screening test for bowel cancer.     

Testing for Heterogeneity with Categorical Data: Permutation Solution vs. Bootstrap Method

In this article the problem of comparing distributional heterogeneities for categorical variables is addressed. Specifically, the one-sided testing problem for heterogeneity comparisons is considered. For such a problem a bootstrap method is proposed and compared with a permutation method already present in literature. The power behavior of the two methods is compared through a Monte Carlo simulation study. The results of two real applications are shown.     

To Aggregate,Pool, or Neither

It is well known that, even if all forecasters are rational, unbiasedness tests using consensus forecasts are inconsistent because forecasters have private information. However, if all forecasters face a common realization, pooled estimators are also inconsistent. In contrast, we show that when predictions and realizations are integrated and cointegrated, microhomogeneity ensures that consensus and pooled estimators are consistent. Therefore, contrary to claims in the literature, in the absence of microhomogeneity, pooling is not a solution to the aggregation problem. We reject microhomogeneity for a number of forecasts from the Survey of Professional Forecasters. Therefore, for these variables unbiasedness can only be tested at the individual level.     

截面相关面板数据的部分异质结构的识别

在大维面板数据中,截面之间很可能呈现出部分异质的特征,即参数在截面间具有组群效应,同组参数相同而不同组参数相异。如果忽略部分异质性而采用完全异质或同质的方法,可能导致估计的不一致性以及统计推断无效性。鉴于已有的部分异质性的研究要么限定截面独立,要么局限于强因子情形,本文尝试在Reese和Westerlund（2015）[1]提出的允许强因子或非强因子存在的较一般的框架下探讨面板数据部分异质结构的识别问题。采用Pesaran（2006）[2] CCE （Common Correlated Effects）方法处理不同强弱的共同因子,并借鉴Su et al.,（2016）[3]的C-Lasso （Classifier- Least Absolute Shrinkage and Selection Operator）方法,对CCE变化后的方程构造带有加法-乘法惩罚项的惩罚最小二乘,优化后以同步地实现分组和参数的估计。理论分析表明,在强因子或半强因子情形中,本文所提方法在分组方面具有渐近一致性,即所有个体被正确分组的概率随着 而趋于1。同时,参数的Lasso估计和事后Lasso估计均具有渐近正态性。另外分析结果也表明,因子的强弱不会影响分组的一致性但会影响以上两种估计量的渐近正态性,因子越强,两种估计量收敛得越快。模拟结果则表明有限样本下,本文所提的方法在分组、参数估计和分组数确定方面均具有良好的表现。具体的,在强因子和不同的半强因子情形中,随着N,T的增加,分组和分组数正确率很快地上升到100%,而两种参数估计的均方根误差和偏差则明显地降低。最后,利用本文所提的方法,研究了人力资本对经济增长影响的部分异质性。     

新世纪新疆汉语文学文化资源和主题精神

新世纪新疆汉语文学需要在保持自身文学优势的前提下,打破创作的思维定势和固有模式,以掌握新的文学机遇。这种双重方向的努力不仅基于对丰富文学资源的尊重,也基于对当代文学主体精神沉沦境况下的迎难而上。新疆当代汉语文学长期以来建立起＂异质性＂的文学身份,这种文学身份对自身未来的发展进行了积极的理性思考。     

基于MCMC稳态模拟的异质性经济增长模型研究

 针对同质性增长模型无法描述各个经济体经济增长存在的异质性现象,提出了一类基于MCMC稳态模拟的异质性经济增长模型,它可以用来描述经济增长的异质性以及政策变量的差异影响。由于模型参数的后验条件分布没有确定的分布形式,通过数据扩充得到参数的完全条件分布从而实现模型参数的贝叶斯估计。对改革开放以来我国各省市区经济增长收敛性进行分析发现大规模股份制改革前经济增长具有同质性而大规模股份制改革后经济增长具有异质性,且可以用新古典经济增长理论来解释各地区经济的发展状况。