Estimation of Nonparametric Models With Simultaneity

We introduce methods for estimating nonparametric, nonadditive models with simultaneity. The methods are developed by directly connecting the elements of the structural system to be estimated with features of the density of the observable variables, such as ratios of derivatives or averages of products of derivatives of this density. The estimators are therefore easily computed functionals of a nonparametric estimator of the density of the observable variables. We consider in detail a model where to each structural equation there corresponds an exclusive regressor and a model with one equation of interest and one instrument that is included in a second equation. For both models, we provide new characterizations of observational equivalence on a set, in terms of the density of the observable variables and derivatives of the structural functions. Based on those characterizations, we develop two estimation methods. In the first method, the estimators of the structural derivatives are calculated by a simple matrix inversion and matrix multiplication, analogous to a standard least squares estimator, but with the elements of the matrices being averages of products of derivatives of nonparametric density estimators. In the second method, the estimators of the structural derivatives are calculated in two steps. In a first step, values of the instrument are found at which the density of the observable variables satisfies some properties. In the second step, the estimators are calculated directly from the values of derivatives of the density of the observable variables evaluated at the found values of the instrument. We show that both pointwise estimators are consistent and asymptotically normal.     

Identification Properties of Recent Production Function Estimators

This paper examines some of the recent literature on the estimation of production functions. We focus on techniques suggested in two recent papers, Olley and Pakes (1996) and Levinsohn and Petrin (2003). While there are some solid and intuitive identification ideas in these papers, we argue that the techniques can suffer from functional dependence problems. We suggest an alternative approach that is based on the ideas in these papers, but does not suffer from the functional dependence problems and produces consistent estimates under alternative data generating processes for which the original procedures do not.     

Strategic Design Responsiveness: An Empirical Analysis of US Retail Store Networks

This study uses a service operations management (SOM) strategy lens to investigate chain store retailers' strategic design responsiveness (SDR)—a term that captures the degree to which retailers dynamically coordinate investments in human and structural capital with the complexity of their service and product offerings. Labor force and physical capital are respectively used as proxies for investments in human capital and structural capital, whereas gross margins are proxies for product/service offering complexity. Consequently, SDR broadly reflects three salient complementary choices of SOM design strategy. We test the effects of “brick and mortar” chain store retailers' SDR on current and future firm performance using publically available panel data collected from Compustat and the University of Michigan American Customer Satisfaction Index databases for the period 1996–2011. We find that retailers that fail to keep pace with investments in both structural and human capital exhibit short‐term financial benefits, but have worse ongoing operational performance. These findings corroborate the importance of managers strategically maintaining the complementarity of design‐related choices for improving and maintaining business performance.     

LABOR SUPPLY OF POLITICIANS

Using data on Members of the European Parliament (MEPs), we examine the impact of salaries on the composition and the behavior of legislators. Employing a differences‐in‐differences approach, we exploit the introduction of a law that equalized MEPs' salaries which had previously differed by as much as a factor of 10. Increasing salaries raises the fraction of MEPs who run for re‐election but decreases the quality of elected MEPs (proxied by college quality). Salary has no discernible impact on effort or legislation output. Higher salaries induce more political competition.     

Coherence principles in interval‐based dose finding

This paper studies the notion of coherence in interval‐based dose‐finding methods. An incoherent decision is either (a) a recommendation to escalate the dose following an observed dose‐limiting toxicity or (b) a recommendation to deescalate the dose following a non–dose‐limiting toxicity. In a simulated example, we illustrate that the Bayesian optimal interval method and the Keyboard method are not coherent. We generated dose‐limiting toxicity outcomes under an assumed set of true probabilities for a trial of n=36 patients in cohorts of size 1, and we counted the number of incoherent dosing decisions that were made throughout this simulated trial. Each of the methods studied resulted in 13/36 (36%) incoherent decisions in the simulated trial. Additionally, for two different target dose‐limiting toxicity rates, 20% and 30%, and a sample size of n=30 patients, we randomly generated 100 dose‐toxicity curves and tabulated the number of incoherent decisions made by each method in 1000 simulated trials under each curve. For each method studied, the probability of incurring at least one incoherent decision during the conduct of a single trial is greater than 75%. Coherency is an important principle in the conduct of dose‐finding trials. Interval‐based methods violate this principle for cohorts of size 1 and require additional modifications to overcome this shortcoming. Researchers need to take a closer look at the dose assignment behavior of interval‐based methods when using them to plan dose‐finding studies.     

Parameter estimation of Lindley step stress model with independent competing risk under type 1 censoring

Abstract

In literature, Lindley distribution is considered as an alternative to exponential distribution to fit lifetime data. In the present work, a Lindley step-stress model with independent causes of failure is proposed. An algorithm to generate random samples from the proposed model under type 1 censoring scheme is developed. Point and interval estimation of the model parameters is carried out using maximum likelihood method and percentile bootstrap approach. To understand the effectiveness of the resulting estimates, numerical illustration is provided based on simulated and real-life data sets.     

Relationships among JIT practices: an interpretive modeling approach

Abstract

This research develops a model of relationships among components of Total-JIT, including JIT-information, JIT-manufacturing, JIT-purchasing, and JIT-selling, to establish an implementation hierarchy based on relative importance. The data collected relates to the relationships among JIT components and two performance measures, supply chain competency and organizational performance. Two groups are used in the research, one group of five operations management academics and another group of 30 practicing operations managers working in U.S. manufacturing firms. An interpretive structural modelling methodology is used to develop alternative structural models. The academics’ data show JIT-information emerging as lynchpin of relationships, directly impacting all other JIT practices and both performance measures. The practitioners’ data indicates that all JIT practices and performance measures are interactive as components and outcomes. This study is the first to apply interpretive structural modelling to investigate the interplay among total-JIT components and the performance measures of supply chain competency and organizational performance.     

Ranking of the Most Prolific Authors,Universities, and Organizations in the Journal of Organizational Behavior Management

ABSTRACT

Over the years, reviews in behavior analysis have sought to identify the most prolific researchers and institutions. The goal of these reviews was to offer one resource for behavior analysts to identify experts in behavior analysis and quality graduate programs. However, most of these reviews omitted the Journal of Organizational Behavior Management (JOBM), making the results less relevant to those who work in organizational behavior management. The purpose of this review was to extend previous findings and identify the most published researchers, academic institutions, and organizations in JOBM since its inception. Furthermore, we calculated the citation rate (per year, per article) for each of the top 20 most published authors. The results, implications, and opportunities for further analysis are discussed.     

贫困地区新生代女性农民工休闲生活现状调查研究--以甘肃省定西市为例

休闲已成为现代人生活、工作所不可或缺的组成部分。作为经济转型时期的特殊社会群体,新生代女性农民工的休闲生活现状值得关注。研究以甘肃省定西市为例,从休闲时间、休闲消费、休闲认知三个维度对本地区新生代女性农民工与男性农民工、同龄城市女青年休闲生活进行对比研究,得出结论:贫困地区新生代女性农民工休闲时间严重不足,主要休闲消费方式仍处于消极型的休闲层次类型;相对于上一代农民工而言,她们已经认识到休闲的重要性,但由于受封闭的休闲空间及拮据的经济条件所限,她们的休闲动机仍停留在马斯洛的五个需求层次中前两层的初级需要。针对此现状,文章提出了相应的对策与建议。      

A log rank type test in observational survival studies with stratified sampling

In randomized clinical trials, the log rank test is often used to test the null hypothesis of the equality of treatment-specific survival distributions. In observational studies, however, the ordinary log rank test is no longer guaranteed to be valid. In such studies we must be cautious about potential confounders; that is, the covariates that affect both the treatment assignment and the survival distribution. In this paper, two cases were considered: the first is when it is believed that all the potential confounders are captured in the primary database, and the second case where a substudy is conducted to capture additional confounding covariates. We generalize the augmented inverse probability weighted complete case estimators for treatment-specific survival distribution proposed in Bai et al. (Biometrics 69:830–839, 2013) and develop the log rank type test in both cases. The consistency and double robustness of the proposed test statistics are shown in simulation studies. These statistics are then applied to the data from the observational study that motivated this research.