Late,But Not Too Late? Postponement of First Birth Among Highly Educated US Women

We examine the link between the postponement of parenthood and fertility outcomes among highly educated women in the USA born in 1920–1986, using data from the CPS June Supplement 1979–2016. We argue that the postponement–low fertility nexus noted in demographic and biomedical research is especially relevant for women who pursue postgraduate education because of the potential overlap of education completion, early career stages, and family formation. The results show that women with postgraduate education differ from women with college education in terms of the timing of the first birth, childlessness, and completed fertility. While the postponement trend, which began with the cohorts born in the 1940s, has continued among highly educated women in the USA, its associations with childlessness and completed parity have changed considerably over subsequent cohorts. We delineate five distinct postponement phases over the 80-year observation window, consistent with variation over time in the prevalence of strategies for combining tertiary education and employment with family formation.     

Application of copulas to multivariate control charts

The most popular multivariate control chart for monitoring the mean of a distribution is probably the Hotelling T² rule. Unfortunately, this rule relies on the assumption that the distribution under control is Gaussian, which is rarely true in practice. The objective of this paper is to propose a new approach for the non-normal multivariate case. It consists in the construction of a tolerance region obtained from a density level set estimation. The method follows a “plug-in” approach in which the density of the observations is previously estimated. This estimation is conducted using copulas modeling, an increasingly popular tool in multivariate modeling.     

Prediction intervals for ordinary and dual generalized order statistics from two independent sequences

ABSTRACT

Based on the observed dual generalized order statistics drawn from an arbitrary unknown distribution, nonparametric two-sided prediction intervals as well as prediction upper and lower bounds for an ordinary and a dual generalized order statistic from another iid sequence with the same distribution are developed. The prediction intervals for dual generalized order statistics based on the observed ordinary generalized order statistics are also developed. The coverage probabilities of these prediction intervals are exact and free of the parent distribution, F. Finally, numerical computations and real examples of the coverage probabilities are presented for choosing the appropriate limits of the prediction.     

Bayesian Analysis of Different Hybrid and Progressive Life Tests

Type-I and Type-II censoring schemes are the widely used censoring schemes available for life testing experiments. A mixture of Type-I and Type-II censoring schemes is known as a hybrid censoring scheme. Different hybrid censoring schemes have been introduced in recent years. In the last few years, a progressive censoring scheme has also received considerable attention. In this article, we mainly consider the Bayesian inference of the unknown parameters of two-parameter exponential distribution under different hybrid and progressive censoring schemes. It is observed that in general the Bayes estimate and the associated credible interval of any function of the unknown parameters, cannot be obtained in explicit form. We propose to use the Monte Carlo sampling procedure to compute the Bayes estimate and also to construct the associated credible interval. Monte Carlo Simulation experiments have been performed to see the effectiveness of the proposed method in case of Type-I hybrid censored samples. The performances are quite satisfactory. One data analysis has been performed for illustrative purposes.     

试论湘西民族地区交通经济带的评价与构建

本文从交通经济带的传统构成要素入手,对湘西民族地区交通基础设施、城镇综合实力、产业状况等进行了评价,提出了以民族文化为纽带构筑民族地区交通经济带的模式,认为该地区可以形成一纵一横两条沿路型经济子带,并提供具体设计思路。     

Statistical Inference Based on Progressively Type II Censored Data from Weibull Model

In this article, we consider the problem of estimating the shape and scale parameters and predicting the unobserved removed data based on a progressive type II censored sample from the Weibull distribution. Maximum likelihood and Bayesian approaches are used to estimate the scale and shape parameters. The sampling-based method is used to draw Monte Carlo (MC) samples and it has been used to estimate the model parameters and also to predict the removed units in multiple stages of the censored sample. Two real datasets are presented and analyzed for illustrative purposes and Monte carlo simulations are performed to study the behavior of the proposed methods.     

The Effects of Ignoring Level Shifts on Systems Cointegration Tests

Summary: In this paper I analyse the effects of ignoring level shifts in the data generating process on systems cointegration tests that do not accommodate level shifts. I consider two groups of Likelihood Ratio tests based on procedures suggested by Johansen (1988) and Saikkonen and Lütkepohl (2000b). The Monte Carlo analysis reveals that ignoring level shifts reduces the tests’ sizes to zero and causes an important drop in the small sample power for increasing shift magnitudes. This suggests that one should apply test procedures, which take account of level shifts. * This paper is a revised and summarized version of Chapter 3 of my PhD thesis (Trenkler, 2002). I would like to thank two anonymous referees for helpful comments on the submitted paper. Furthermore, I am grateful to Christian Müller, Ralf Brüggemann, and Helmut Lütkepohl for many useful suggestions and comments on an earlier version of the paper and the corresponding chapter of my thesis. The research was supported by the Deutsche Forschungsgemeinschaft (DFG) through the SFB 373 “Quantification and Simulation of Economic Processes” and the SFB 649 “Economic Risk”.     

从文化生态学角度解读《诗经·国风》中的桑意象

在现有的《诗经·国风》"桑意象"研究文献的基础上,利用文化生态理论来剖析"桑意象"所具有重要的理论和实践意义.以文化生态学为理论指导,试图揭示《诗经·国风》中"桑意象"的文化内涵不断丰富、演变的历史动态过程,认为桑意象的形成、发展和演变的历史轨迹是:桑树—桑女/女子—爱情/母亲—家园.从文化生态理论中关于人、环境和文化的互动交织关系角度,进一步探讨了桑意象演变的文化生态原因,主要包括自然环境、桑树崇拜、土地崇拜、生殖崇拜,另外"桑"与周代人口政策、社会发展密切相关.     

沙打旺当年播种结实试验观察

进行了沙打旺当年播种结实试验，结果表明：当年播种沙打旺，出苗到种子成熟约需140元左右，播种期不能晚于5月上旬，666.7米2可产粒4.2公斤。