Duration dependence in US business cycles: An analysis using the modulated power law process

The modulated power law process is used to analyze the duration dependence in US business cycles. The model makes less restricting assumptions than traditional models do and measures both the local and global performance of business cycles. The results indicate evidence of positive duration dependence in the U.S. business cycles. Structural change after WWII in both expansion and contraction phases of business cycles is also documented. Hypothesis tests confirm that the model fits US business cycles.      

Bathtub-shaped failure rate functions

The failure rate function is an important quantity characterizing life phenomena. Ideally, one would expect this function to exhibit a bathtub shape. In this paper, a comprehensive review of the known distributions that exhibit this shape is provided. Over 17 such distributions are identified. This review is especially important because almost all of the commonly known distributions in statistics do not exhibit the bathtub shape. Furthermore, it could serve as an important reference and encourage developments of further distributions that exhibit a bathtub shape.     

An Example of Data Technology Product: A Control Chart for Weibull Processes

This work proposes a new Shewhart-type control chart of the Weibull percentile (i.e. the reliable life) as a practical example of a product attained following the Data Technology (DT) approach. DT is briefly introduced as a new discipline defined apart from Information Technology (IT). Following this approach, some specific Bayes estimators are selected from literature and then used to build the above new chart. These estimators allow to improve the control making use of any available kind of data (statistical and non-statistical). The operative steps of DT approach are fully explained. The results are illustrated by means of a real applicative example.     

A new condition for identifiability of finite mixture distributions

In this paper a sufficient condition for the identifiability of finite mixtures is given. This condition is less restrictive than Teicher’s condition Teicher H, Ann Math Stat 34:1265–1269 (1963) and therefore it can be applied to a wider range of families of mixtures. In particular, it applies to the classes of all finite mixtures of Log-gamma and of reversed Log-gamma distributions. These families have been already studied by Henna J Jpn Stat Soc 24:193–200 (1994) using another condition, different from Teicher’s, but more difficult to check in many cases. Furthermore, the result given in this paper is very appropiated for the case of mixtures of the union of different distribution families. To illustrate this an application to the class of all finite mixtures generated by the union of Lognormal, Gamma and Weibull distributions is given, where Teicher’s and Henna’s conditions are not applicable     

城市住宅使用寿命研究

在分析了不同寿命数据分析处理的基础上,对住宅使用寿命计算威布尔模型的特点、分布拟合检验、分布参数的点估计和区间估计进行了理论分析和推导。然后结合实证数据构建了中国城市住宅不同年代的使用寿命模型,得出中国城市住宅平均使用寿命偏低及呈现与年代相关的特点。20世纪60年代的住宅平均使用寿命仅为25.5年,70年代住宅为35.7年,80年代为40.4年。并通过调查得出结论,住宅短命的各种原因中经济社会原因占56%。     

Definition of full-time and part-time employment,and distributional assumptions: the implications for the estimated full-time and part-time wage equations

This paper demonstrates that rejecting the standard definition of full-time and part-time workers, the estimated number of hours that an individual is likely to work as a full-time worker is a function of the type of distribution one assumes about the error term in the wage equation. Adopting a switching regression model with unknown sample selection, we have found that the normality assumption generates higher hours for full-timers in comparison with the non-normal distributions. We also noted that regardless of the distribution assumed, the hours differ from one industry to another. The implication is that the standard definition of full-time and part-time worker may not be appropriate for all firms irrespective of the distribution assumed. The paper also shows the sensitivity of parameter estimates to the distributional assumptions about the error term in the wage equation. The results indicate that the normal distribution wage equation estimates are relatively larger than the Weibull and exponential distributions. This finding is particularly important because such differences in estimated coefficients may have a direct wage influence on the wage gap between full-time and part-time workers across distributions.     

遵从科创规律：再谈科创成果与年龄的关系

本文回顾了“成果-年龄”研究的历史和逻辑，系统梳理了相关研究，讨论了该理论模型存在的问题和下一步发展方向。认为“成果-年龄”理论模型在宏观和中观层次上具有一定同构性，可以借鉴“介尺度”思想方法，将威布尔分布统计规律在微观层次尝试。建议要遵从科创规律，保障科创群体工作时间和专注力，在最适合出成果的年龄专心搞研究。