On panel data filtering in technical efficiency estimation

In present days it is commonly recognized that firm production datasets are affected by some level of random perturbation, and that consequently production frontiers have a stochastic nature. Mathematical programming methods, traditionally employed for frontier evaluation, are then reputed capable of mistaking errors for technical (in)efficiency. Therefore, recent literature is oriented towards a statistical view: frontiers are designed by enveloping data that have been preliminarly filtered from noise.In this paper a nonparametric smoother for filtering panel production data is presented. We pursue a recent approach of Kneip and Simar (1996), and frame it into a more general formulation whose a setting constitutes our specific proposal. The major feature of the method is that noise reduction and outlier detection are faced separately: i) a high order local polynomial fit is used as smoother; and ii) data are weighted by robustness scores. An extensive numerical study on some common production models yields encouraging results from a competition with Kneip and Simars filter.     

Homocysteine, menopause and cardiovascular disease

A high plasma concentration of total homocysteine (tHcy) and a deficiency of vitamins related to its metabolism, such as vitamin B12 and folate, have been associated with cardiovascular disease. Postmenopausal women have higher concentrations than age-matched premenopausal women, and plasma concentrations of homocysteine in postmenopausal women taking hormone replacement therapy are significantly lower than they are in those who do not take estrogen supplements. Because of the possible mixed effects of HRT on cardiovascular events, surrogate end-points must be evaluated with caution. While measuring homocysteine levels is relatively simple, evidence from well designed trials is awaited before population screening can be advocated. Also, the benefits of reducing homocysteine levels with folic acid and vitamin B6 and B12 supplements are highly debated.     

Wo sind die Bachelorabsolventen heute und wie sehen sie ihr Studium?

The paper is based on a survey of graduates of the BA course Social Sciences at the Heinrich-Heine-University Düsseldorf. The course, which is a combination of Sociology, Political Science and Communication and Media Studies, was set up in 1999. In 2002 the first students completed the course. Therefore, the BA course Social Sciences is one of the BA courses with the longest experience in Germany. Four graduate years were interviewed for the survey. The aim of the survey was to find out where the graduates now stand and how they judge the course in retrospect. The results show that half of the graduates currently have an occupation, slightly over a third is doing a Master’s degree and about 10 % are in a temporary situation or performing other activities. Overall, the graduates are satisfied with the course. The evaluation of the individual course elements shows the strengths and weaknesses of the course.     

Impact of Religiosity on the Sexual Risk Behaviors of Young Men Who Have Sex With Men

Young men who have sex with men (YMSM), particularly Black YMSM, bear a disproportionate burden of new human immunodeficiency virus (HIV) infections in the United States. Several studies support the positive and protective role of religion in health and the prevention of morbidity and mortality. However, little empirical research has been conducted looking at religion with the context of YMSM and HIV prevention. We examined the impact of religious attendance and faithfulness on sexual risk among a community-based sample of 450 YMSM in Chicago ages 16 to 20. Participants were mostly racial/ethnic minorities, that is, Black (53.4%) and Latino (19.9%). Multivariate logistic regression indicated that faithfulness in combination with frequent formal religious attendance was associated with a decrease in reported number of unprotected anal sex acts, including unprotected receptive anal sex with male partners. These association trends were also found for the Black YMSM in our sample, suggesting that religious involvement and faithfulness is a potential protective factor for the acquisition of HIV among this high-risk population.     

The French republican model of integration: the theory of cohesion and the practice of exclusion

What are the explaining factors for the wave of riots in France in November 2005? In providing some answers, this article begins by examining the practical usefulness of the French republican model of integration for social cohesion, highlighting the way its negation of other criteria, such as ethnicity, race, or religion, limit this national conception of citizenship and emphasizing these excluded factors as one of the main causes of frustration and resentment among migrant groups in France.The author compares these riots to the student movements in spring 2006 and shows some similarities as well as important differences between the explaining structural factors of these two youth-based social upheavals. One of the contributing distinctions is the experience of ethnic and racial discrimination as an important source of deep resentment. The author avoids reducing the riots simply to a clash between ethnic groups with specific ethnic interests or a class revolt. Instead, he stresses the relationship between specific social structural factors and spatial effects as the element that created the context for the riots by transforming inequalities into visible and indefensible discrimination. Several factors show that spatial aspects (in the form of segregation) are important alongside the ethnic/racial ones in explaining the riots.     

DOES DIVORCE LAW MATTER?

In this paper we derive an explicit model of negotiations between spouses when unconstrained transfers are possible only in case of separation. We show that inefficient separation may occur in equilibrium even under consensual divorce law. This provides theoretical support for the view that changes in social norms rather than in legislation may be responsible for increasing divorce rates. (JEL: C78, J120)     

Weighted likelihood based inference for P(X < Y)

This contribution deals with the statistical problem of evaluating the stress–strength reliability parameter R = P(X < Y), when both stress and strength data are prone to contamination. Standard likelihood inference can be badly affected by mild data inadequacies, that often occur in the form of several outliers. Then, robust tools are recommended. Here, inference relies on the weighted likelihood methodology. This approach has the advantage to lead to robust estimators, tests, and confidence intervals that share the main asymptotic properties of their classical counterparts. The accuracy of the proposed methodology is illustrated both by numerical studies and real-data applications.