基于农民工“过渡性”特点的刘易斯转折点分析

本文以二元经济理论为基础,从农民工的过渡性特点出发,利用改造后的刘易斯模型分析我国劳动力转移现状,解释了民工潮和民工荒交替发生的原因,结论认为当前农民工的工资上涨是在剩余劳动力数量依然庞大和工资水平极低的背景下发生的,从而认为我国的刘易斯转折点还没有到来,应把关注重点放在如何尽快实现农民工市民化和加快城市化进程上来。     

我国是否进入“刘易斯转折点”——文献述评及思考

本文梳理已有研究文献,将关于我国是否进入刘易斯转折点的观点归纳为三种:第一种观点认为我国已全面进入刘易斯转折点阶段;而第二种观点持相反意见,认为民工荒是特殊背景下的结构性失衡现象,我国农村劳动力供大于求的总体态势不会轻易发生逆转;第三种观点则认为我国经济处于中国特色的刘易斯转折点区间内。从不同视角认识这些争论有助于我们更好地把握刘易斯转折点,应对日益严峻的民工荒现象,更好地利用和兑现人口红利以及做好迎接刘易斯转折点的准备,实现我国经济由二元结构向一元结构的协调转型。     

On the Local Polynomial Estimators of the Counting Process Intensity Function and its Derivatives

Abstract. We consider the properties of the local polynomial estimators of a counting process intensity function and its derivatives. By expressing the local polynomial estimators in a kernel smoothing form via effective kernels, we show that the bias and variance of the estimators at boundary points are of the same magnitude as at interior points and therefore the local polynomial estimators in the context of intensity estimation also enjoy the automatic boundary correction property as they do in other contexts such as regression. The asymptotically optimal bandwidths and optimal kernel functions are obtained through the asymptotic expressions of the mean square error of the estimators. For practical purpose, we suggest an effective and easy‐to‐calculate data‐driven bandwidth selector. Simulation studies are carried out to assess the performance of the local polynomial estimators and the proposed bandwidth selector. The estimators and the bandwidth selector are applied to estimate the rate of aftershocks of the Sichuan earthquake and the rate of the Personal Emergency Link calls in Hong Kong.     

Convergence in distribution of multiple change point estimators

In this paper we establish the asymptotic distribution for a class of multiple change point estimators in the following setup: a finite sequence of independent random variables consists of segments given by a known number of so-called change points such that the underlying distribution differs from segment to segment. In a nonparametric framework the proposed estimator is defined as the maximizing point of weighted multivariate U-statistic processes. We show that the proposed estimators converge in distribution to a maximizer of a sum of random walks with drift.     

论内丹学体系的逻辑建构

内丹学是中国古代历史悠久的生命哲学,也是道教中占有重要地位的修道理论。其理论的核心是:何以通过内丹修炼能够超越个体生命限度,达成长生,以及如何通过内丹修炼达成长生的问题。关于内丹学理论,近年来已经有很多的专家学者从不同角度作出了大量卓有成效的研究,但在内丹学理论体系的逻辑建构方面犹有所未及者。因此,从思辨逻辑的视角来考察钟吕系金丹派经由对历史上长生众术的批判、内丹学轴心范畴和逻辑起点范畴的确立以及内丹学体系的自我论证四个环节建构内丹学理论体系的过程具有重要的理论价值。     

从战争经济学看二战历史转折点

我国的历史研究中,习惯上将前苏联的斯大林格勒保卫战当成第二次世界大战的转折点.但从影响战局的最重要的因素-政治经济实力对比看,珍珠港事件更应当作为二战历史的转折点来看待.     

多维视野中的壮侗民族建筑文化

以干栏式民居、鼓楼、风雨桥等建筑为代表的物质性文化,以营造技术、装饰工艺、居住方式为载体的行为性文化和以建筑仪式、居住信仰、习俗及审美情趣等观念性文化构成的建筑文化体系,是壮侗民族在长期的社会生活实践中因地制宜、富于创造、不断积累而形成的,是壮侗民族传统文化的重要组成部分,凝聚着壮侗民族的智慧与创造精神,其中蕴含着丰富的文化内涵,具有重要的历史、文化和学术价值。本文以多维的视野,对壮侗民族建筑文化的内涵及其价值进行揭示。     

Existence and Uniqueness of Solutions to the Bellman Equation in the Unbounded Case

We study the problem of the existence and uniqueness of solutions to the Bellman equation in the presence of unbounded returns. We introduce a new approach based both on consideration of a metric on the space of all continuous functions over the state space, and on the application of some metric fixed point theorems. With appropriate conditions we prove uniqueness of solutions with respect to the whole space of continuous functions. Furthermore, the paper provides new sufficient conditions for the existence of solutions that can be applied to fairly general models. It is also proven that the fixed point coincides with the value function and that it can be approached by successive iterations of the Bellman operator.     

Key considerations for choosing a statistical method to deal with incomplete treatment adherence in pragmatic trials

Pragmatic trials offer practical means of obtaining real-world evidence to help improve decision-making in comparative effectiveness settings. Unfortunately, incomplete adherence is a common problem in pragmatic trials. The commonly used methods in randomized control trials often cannot handle the added complexity imposed by incomplete adherence, resulting in biased estimates. Several naive methods and advanced causal inference methods (e.g., inverse probability weighting and instrumental variable-based approaches) have been used in the literature to deal with incomplete adherence. Practitioners and applied researchers are often confused about which method to consider under a given setting. This current work is aimed to review commonly used statistical methods to deal with non-adherence along with their key assumptions, advantages, and limitations, with a particular focus on pragmatic trials. We have listed the applicable settings for these methods and provided a summary of available software. All methods were applied to two hypothetical datasets to demonstrate how these methods perform in a given scenario, along with the R codes. The key considerations include the type of intervention strategy (point treatment settings, where treatment is administered only once versus sustained treatment settings, where treatment has to be continued over time) and availability of data (e.g., the extent of measured or unmeasured covariates that are associated with adherence, dependent confounding impacted by past treatment, and potential violation of assumptions). This study will guide practitioners and applied researchers to use the appropriate statistical method to address incomplete adherence in pragmatic trial settings for both the point and sustained treatment strategies.     

Phase I monitoring of social network with baseline periods using poisson regression

Social network analysis is an important analytic tool to forecast social trends by modeling and monitoring the interactions between network members. This paper proposes an extension of a statistical process control method to monitor social networks by determining the baseline periods when the reference network set is collected. We consider probability density profile (PDP) to identify baseline periods using Poisson regression to model the communications between members. Also, Hotelling T² and likelihood ratio test (LRT) statistics are developed to monitor the network in Phase I. The results based on signal probability indicate a satisfactory performance for the proposed method.