Nonparametric covariate adjustment for receiver operating characteristic curves

The accuracy of a diagnostic test is typically characterized using the receiver operating characteristic (ROC) curve. Summarizing indexes such as the area under the ROC curve (AUC) are used to compare different tests as well as to measure the difference between two populations. Often additional information is available on some of the covariates which are known to influence the accuracy of such measures. The authors propose nonparametric methods for covariate adjustment of the AUC. Models with normal errors and possibly non‐normal errors are discussed and analyzed separately. Nonparametric regression is used for estimating mean and variance functions in both scenarios. In the model that relaxes the assumption of normality, the authors propose a covariate‐adjusted Mann–Whitney estimator for AUC estimation which effectively uses available data to construct working samples at any covariate value of interest and is computationally efficient for implementation. This provides a generalization of the Mann–Whitney approach for comparing two populations by taking covariate effects into account. The authors derive asymptotic properties for the AUC estimators in both settings, including asymptotic normality, optimal strong uniform convergence rates and mean squared error (MSE) consistency. The MSE of the AUC estimators was also assessed in smaller samples by simulation. Data from an agricultural study were used to illustrate the methods of analysis. The Canadian Journal of Statistics 38:27–46; 2010 © 2009 Statistical Society of Canada     

Duality of the improved algebraic method (DIAM)

In this note we present a variant of the improved algebraic method (IAM) using a duality analysis to solve linear programming (LP) problems where more insights to the method are presented. When the coordinates of all vertices are computed, any feasible point can be expressed as a linear combination of the vertices. The objective function is expressed as a weighted sum of its evaluation at the feasible vertices and the optimal point is associated with the highest/lowest coefficient of the weighted sum.     

Revolutionary Horizons: Past and Present in Bolivian Politics

Revolutionary Horizons, by Forrest Hylton and Sinclair Thomson,is a highly readable work that contributes to understandingthe recent events that have placed Bolivia, once erased fromthe map by Queen Victoria following the expulsion of her emissaryin the nineteenth century, in the spotlight of observers ofprogressive movements around the world. With an insightful introductionby Adolfo Gilly, the book provides an accessible analysis ofthe events that led to the inauguration of Evo Morales, thefirst indigenous president in Bolivian history, in January 2006,ending the epoch of Andean apartheid. More than a simple recounting,     

Designing a Programme to Support Smallholder Agriculture in Mexico: Lessons from PROCAMPO and Oportunidades

This article argues that there is a gap in current Mexican rural development policy that could be filled by a smallholder‐targeted programme. The gap exists because agricultural programmes tend to benefit better‐off farmers, while social programmes tend to focus on long‐term investment in human capital, specifically for the children of today's poor. Drawing on lessons from PROCAMPO and Oportunidades, it offers a specific design for such a programme at a time when the government is considering how to reform PROCAMPO, given that, after 15 years, it is due to come to an end.     

Evaluation of an upper extremity student-role functioning scale using item response theory

Millions of workers suffer from upper extremity (musculoskeletal) disorders. Many of these workers are predisposed to upper extremity musculoskeletal disorders because of early exposure to ergonomic risks as students. Computer usage for four or more hours remains the greatest risk for upper extremity musculoskeletal disorders for workers and students alike. Developing preventative methods to reduce student exposure, and thus protect future workers from upper extremity musculoskeletal disorders later in life, requires an appropriate measure for upper extremity musculoskeletal disorder prevalence and related limitations for student functioning. Item response theory analysis was used to evaluate and further develop a upper extremity functioning scale for the student role.     

Introduction: moving youth participation forward

Given the emerging interest among researchers, practitioners, and policymakers in youth participation, it is important to examine and assess carefully the promise and challenges of youth engagement.     

The influence of top management corporate networks on CEO succession

We analyze empirically how supervisory board members with multiple directorships affect the decision to hire an inside or outside CEO successor. While a growing number of both theoretical and empirical studies analyze the influence of corporate performance and size or the ownership structure on this decision, the role of multiple board memberships within the CEO recruitment process has been widely neglected so far. The present study is based on panel data of the largest German companies covering the period from 1996 to 2008. Applying competing risk estimations we find a weak and positive association between the number of external directorships of the supervisory board members and internal CEO replacements. Distinguishing between different groups of external board positions, we find that external executives on the supervisory board increase the likelihood of external CEO replacements. In line with empirical findings for the US we argue that external executives improve the assessment of potential CEO successors leading to more outside CEO replacements. In contrast, we find evidence that external supervisory board mandates of the supervisory board members cause more internal CEO replacements. This finding indicates a substitution of external expertise of the executives by multiple supervisory board mandates but could also reflect a reduction of the monitoring intensity of the supervisory board.     

An Empirical Investigation of Terrorism-induced Stress on Expatriate Attitudes and Performance

Despite international terrorism's increasing relevance for international business, the effects of terrorism that confront employees during assignments abroad have hardly been investigated. Applying a stress perspective, this article analyzes the impact of terrorism-induced stress on attitudes and the performance of expatriates. Employing data from 143 expatriate managers in high-risk countries, the study shows that several terrorism-related stressors create a significant stress level for the individual, causing negative work attitudes and attitudes towards host country nationals (disaffection). This eventually leads to worse performance. We applied partial least squares (PLS) structural equation modeling (SEM) to analyze the entire impact path and found substantial support for our hypotheses. Of all the relevant stressors, intra-family conflicts due to terrorism have the greatest impact.     

Insider ownership and corporate performance: evidence from Germany

In this paper we address the question whether insider ownership affects corporate performance. Evidence from studies dealing with Anglo-Saxon countries is rather inconclusive, especially because results seem to be significantly affected by endogeneity. Economically, this is due to the fact that in these countries insider ownership seems to be mainly driven by management’s compensation contracts. We argue that Germany is different in this regard, as insider ownership is often related to family control, stock-based compensation is less widespread, and the market for corporate control used to be less developed. Starting from this presumption, our data allows an unbiased observation as to whether insider ownership affects firm performance. Using a pooled data set of 648 firm observations for the years 2003 and 1998, we find evidence for a positive and significant relationship between corporate performance—as measured by stock price performance, market-to-book ratio and return on assets—and insider ownership. This relationship seems to be rather robust, even if we account for potential endogeneity by applying a 2SLS regression approach. Furthermore, the results hold for a sub-sample of firms that did not have a stock-based compensation program in place. Moreover, we find outside block ownership as well as more concentrated insider ownership to have a positive impact on corporate performance. Overall, the results indicate that ownership structure might be an important variable explaining the long term value creation in the corporate sector.

Forecasting mortality rates via density ratio modeling

The authors propose a semiparametric approach to modeling and forecasting age‐specific mortality in the United States. Their method is based on an extension of a class of semiparametric models to time series. It combines information from several time series and estimates the predictive distribution conditional on past data. The conditional expectation, which is the most commonly used predictor in practice, is the first moment of this distribution. The authors compare their method to that of Lee and Carter.