Modelling period fertility: Schooling and intervals following a birth in Eastern Africa

We describe a regression-based approach to the modelling of age-, order-, and duration-specific period fertility, using retrospective survey data. The approach produces results that are free of selection biases and can be used to study differential fertility. It is applied to Demographic and Health Survey data for Ethiopia, Kenya, Tanzania, and Zimbabwe to investigate differential trends in fertility by education. Parity progression fell and the intervals following each birth lengthened between the 1970s and 2000s in all four countries. Fertility fell most among women with secondary education. In contrast to other world regions, postponement of successive births for extended periods accounted for much of the initial drop in fertility in these African countries. However, family size limitation by women with secondary education in Ethiopia and Kenya and longer birth spacing in Zimbabwe also played significant roles. Thus, birth control is being adopted in Eastern Africa in response to diverse changes in fertility preferences.     

闻一多新诗中的民族化建构思想研究

强调中西艺术的融会贯通,这是闻一多的一贯主张。闻一多认为,只有时时刻刻想着我是个中国人,才能做出真正的中国的新诗,因此,在他短暂的诗歌创作生涯中,他始终把新诗的民族性建构作为旨归并长期躬耕于此,他的诗歌表现了对民族历史与文化的关注,对祖国的热爱与对祖国命运的忧虑,对人民命运的同情与对黑暗势力的控诉,在内在精神方面呈现出显著的民族性。     

从苏童的《妻妾成群》探究中国的女性权力问题

本文分析苏童小说《妻妾成群》,深刻地揭示了女性生存权力的抗争。     

Use of log−log survival function in modeling time-covariate interactions in Cox regression

Plotting of log−log survival functions against time for different categories or combinations of categories of covariates is perhaps the easiest and most commonly used graphical tool for checking proportional hazards (PH) assumption. One problem in the utilization of the technique is that the covariates need to be categorical or made categorical through appropriate grouping of the continuous covariates. Subjectivity in the decision making on the basis of eye-judgment of the plots and frequent inconclusiveness arising in situations where the number of categories and/or covariates gets larger are among other limitations of this technique. This paper proposes a non-graphical (numerical) test of the PH assumption that makes use of log−log survival function. The test enables checking proportionality for categorical as well as continuous covariates and overcomes the other limitations of the graphical method. Observed power and size of the test are compared to some other tests of its kind through simulation experiments. Simulations demonstrate that the proposed test is more powerful than some of the most sensitive tests in the literature in a wide range of survival situations. An example of the test is given using the widely used gastric cancer data.     

农村人口流迁动因研究评说

关于乡—城人口流迁的动因,历来为国内外学者所重视,研究成果颇多。那么迄今为止,都有哪些关于人口流迁动因的理论和观点?这些理论和观点能否完全解释20世纪80年代中后期中国的农村人口流迁现象?这些众多的理论和观点可以概括为三种:第一,宏观社会结构影响说;第二,生存与发展困境说;第三,劳动力剩余说。这三派观点各自都在自己所限定的范围内从一般意义上较为可信地解释了农村人口流迁的原因,但是由于方法论上的整体主义与个体主义的矛盾等原因,这些观点又有其局限性,因此,我们在借鉴这些观点解释20世纪80年代中后期以来中国农民的流迁动因的时候,应持审慎的态度。     

Temporal prediction of future state occupation in a multistate model from high-dimensional baseline covariates via pseudo-value regression

In many complex diseases such as cancer, a patient undergoes various disease stages before reaching a terminal state (say disease free or death). This fits a multistate model framework where a prognosis may be equivalent to predicting the state occupation at a future time t. With the advent of high-throughput genomic and proteomic assays, a clinician may intent to use such high-dimensional covariates in making better prediction of state occupation. In this article, we offer a practical solution to this problem by combining a useful technique, called pseudo-value (PV) regression, with a latent factor or a penalized regression method such as the partial least squares (PLS) or the least absolute shrinkage and selection operator (LASSO), or their variants. We explore the predictive performances of these combinations in various high-dimensional settings via extensive simulation studies. Overall, this strategy works fairly well provided the models are tuned properly. Overall, the PLS turns out to be slightly better than LASSO in most settings investigated by us, for the purpose of temporal prediction of future state occupation. We illustrate the utility of these PV-based high-dimensional regression methods using a lung cancer data set where we use the patients’ baseline gene expression values.     

Effects of some design factors on the distribution of similarity indices in cluster analysis

This article investigates the effects of number of clusters, cluster size, and correction for chance agreement on the distribution of two similarity indices, namely, Jaccard and Rand indices. Skewness and kurtosis are calculated for the two indices and their corrected forms then compared with those of the normal distribution. Three clustering algorithms are implemented: complete linkage, Ward, and K-means. Data were randomly generated from bivariate normal distributions with specified means and variance covariance matrices. Three-way ANOVA is performed to assess the significance of the design factors using skewness and kurtosis of the indices as responses. Test statistics for testing skewness and kurtosis and observed power are calculated. Simulation results showed that independent of the clustering algorithms or the similarity indices used, the interaction effect cluster size x number of clusters and the main effects of cluster size and number of clusters were found always significant for skewness and kurtosis. The three way interaction of cluster size x correction x number of clusters was significant for skewness of Rand and Jaccard indices using all clustering algorithms, but was not significant using Ward's method for both Rand and Jaccard indices, while significant for Jaccard only using complete linkage and K-means algorithms. The correction for chance agreement was significant for skewness and kurtosis using Rand and Jaccard indices when complete linkage method is used. Hence, such design factors must be taken into consideration when studying distribution of such indices.     

Asymptotic inference in poverty indices: an empirical processes approach

We derive an empirical poverty index containing most of those proposed in the literature. Then, we study its asymptotic behavior by using empirical processes theory. From the results obtained, we derive a Wald-type test for comparing a vector of theoretical poverty indices to a vector of reference indices. We study the test statistic under the null hypothesis of equality, fixed alternatives, and a sequence of local alternatives. A simulation experiment conducted shows that our test performs well for exponential and Pareto data.     

科技力与区域金融综合竞争力的模糊曲线分析

针对区域金融研究现状的不足,利用复杂系统原理,建立了全面、客观的金融综合竞争力指标体系,将其分为显示性指标和解释性指标两部分,选取31个地区作为样本,运用主成分和因子分析法对各个区域的金融成长状况进行计量分析研究和排序,并在此基础上进行聚类分析;在解释性指标的模糊曲线分析中,选取科技力指标,通过分析得出该指标以及构成该指标的各个分力与金融综合竞争力存在显著相关关系。科技力对区域金融综合竞争力的解释力和贡献率很高,因此科技力量对金融的发展水平起着决定性作用。