On the NEH heuristic for minimizing the makespan in permutation flow shops

Over the last 20 years the NEH heuristic of Nawaz, Enscore, and Ham published in this journal has been commonly regarded as the best heuristic for minimizing the makespan in permutation flow shops. In recent years some authors claimed to develop new heuristics that are competitive or outperform NEH. Our study reveals that these claims are not justified. We also address the issue of a fair comparison of the NEH results with those obtained by metaheuristics. Finally we conduct a thorough analysis of NEH leading to its modification which secures the optimality in the two-machine case and improves the general performance.     

Subjective Welfare, Well-Being, and Self-Reported Food Hypersensitivity in Four European Countries: Implications for European Policy

This study estimates the effects of food hypersensitivity on individuals?? perceived welfare and well-being compared to non-food hypersensitive individuals. Study respondents were recruited in the Netherlands, Poland, Spain and UK. The difference in welfare between food hypersensitive respondents and those asymptomatic to foods was estimated using a subjective welfare approach, including income evaluation. Well-being was measured using the Cantril Ladder-of-Life Scale, and health status using the Self-Perceived Health Scale. The difference in well-being, welfare and health status between participant groups was explained further using a number of background variables. No significant within-country differences in welfare between food hypersensitive respondents and respondents asymptomatic to foods were found. In terms of well-being, adult food hypersensitive respondents and their spouses reported significantly less happiness than respondents and their spouses asymptomatic to foods in the Netherlands and Poland. In Spain, the spouses of the food hypersensitive respondents were significantly less happy than respondents aymptomatic to foods. The well-being of children did not significantly differ between groups. The degree of severity of food hypersensitivity was negatively related to overall health status. In Poland, food hypersensitive respondents reported worse health status compared to asymptomatic respondents. In Spain, the converse was true. Food hypersensitive respondents were generally less happy with their life as a whole than respondents asymptomatic to foods, presumably because they experienced more negative effects, which were not related to perceived health status.     

The Influence of Social Desirability Pressures on Expressed Immigration Attitudes*

Objective. Immigration scholars have found that the highly educated and political liberals are considerably less likely to support restrictionist immigration policies than other groups. I ask whether the influence of social desirability pressures in the survey interview is responsible for this finding. Methods. An unobtrusive questioning technique known as the list experiment is used to measure Americans' support for immigration restrictionism. The list experiment can easily be embedded in a standard telephone survey and has been used by previous investigators to study racial attitudes. Results. Restrictionist sentiments are found to be more widespread among the U.S. populace than previous studies have estimated, especially among college graduates and political liberals. Conclusion. My findings have implications for immigration scholars and social scientists who study other sensitive attitudes and behaviors. The most commonly employed strategies to reduce socially desirable responding may not be enough.     

New HEAVY Models for Fat-Tailed Realized Covariances and Returns

ABSTRACT

We develop a new score-driven model for the joint dynamics of fat-tailed realized covariance matrix observations and daily returns. The score dynamics for the unobserved true covariance matrix are robust to outliers and incidental large observations in both types of data by assuming a matrix-F distribution for the realized covariance measures and a multivariate Student's t distribution for the daily returns. The filter for the unknown covariance matrix has a computationally efficient matrix formulation, which proves beneficial for estimation and simulation purposes. We formulate parameter restrictions for stationarity and positive definiteness. Our simulation study shows that the new model is able to deal with high-dimensional settings (50 or more) and captures unobserved volatility dynamics even if the model is misspecified. We provide an empirical application to daily equity returns and realized covariance matrices up to 30 dimensions. The model statistically and economically outperforms competing multivariate volatility models out-of-sample. Supplementary materials for this article are available online.     

Validation Theory and Research for a Population-Level Measure of Children’s Development,Wellbeing, and School Readiness

This paper delineates general validity and research questions that are underlying an ongoing program of research pertaining to the Early Development Instrument (EDI, Janus and Offord 2007), a population-level measure, on which teachers rate kindergarten children’s developmental outcomes in the social, emotional, physical, cognitive, and communicative domains. It describes the large-scale research projects that are using the EDI to measure children’s developmental outcomes for entire populations (e.g., provinces, cities). Given the uniqueness of the EDI’s use as monitoring tool, or social indicator, for children’s developmental health at an early age, we spell out the opportunities and challenges that these projects provide with regard to validation research. The article sets the stage for the special issue, as it is dedicated to showcase the different aspects of the conceptual, theoretical, and empirical validation research as well as the collaborative community-based projects that are currently being undertaken with respect to the EDI.     

A note on generalized ridge estimators

It is shown that a necessary and sufficient condition derived by Farebrother (1984)for a generalized ridge estimator to dominate the ordinary least-squares estimator with respect to the mean-square-error-matrix criterion in the linear regression model admits a similar interpretation as the well known criterion of Toro-Viz-carrondo and Wallace (1968)for the dominance of a restricted least-squares estimator over the ordinary least-squares estimator. Two other properties of the generalized ridge estimators, referring to the concept of admissibility, are also pointed out.     

Bounded leadership: An empirical study of leadership competencies,constraints, and effectiveness

Contrary to the previous leadership theories, which focus on specific and narrow aspects of leadership such as employee characteristics, leader’s authenticity, or boundary spanning, the bounded leadership theory is a broad and complex concept. It takes simultaneously many constraints, which are related to activities on an individual, team, organization, and stakeholder level. This study applies the bounded leadership theory to analyze the leadership constraints as the mediator of the relationship between leadership competencies and effectiveness. Our findings show that leaders’ competencies are not enough for them to be effective. Specific competencies enable leaders to overcome the set of constraints and then to increase their effectiveness.