Microdata Access and Labor Market Research: The U. S. Experience

Summary: The paper illustrates the value of broad researcher access to survey and administrative microdata using examples drawn from the U. S. experience, outlining how analyses of trends in earnings inequality, poverty and employment dynamics using such data have benefited policy makers and contributed to improvements in statistical agency data products. Methods of facilitating researcher access, including the release of public use files, the use of licensing agreements, and the establishment of research data centers, are discussed. * The author thanks Anne Polivka, Marilyn Seastrom and two anonymous referees for helpful comments on an earlier draft of the paper.     

MILITIAS AT THE MILLENNIUM:

Critically important to Neil Smelser's theory of collective behavior is the idea that people join radical social movements because they experience strain. A social movement arises to reassure participants that something is being done to redress the underlying source of strain. Militia presence and activity on the Internet (especially Usenet) is a phenomenon that can be studied within Smelser's framework. Militia watchers contend that those who join the militias have experienced the kinds of strain to which Smelser refers. The purpose of this article is to analyze the content of Internet traffic of U.S. militias in order to test the thesis outlined above. It uses militia Web sites and militia messages posted to Usenet (N = 1,196) as primary data to test Smelser's theory. Information was gathered on 171 men and women from 28 U.S. militias who posted messages to Usenet from 1998–2001. Based on the militiamen/women studied, Smelser's thesis is generally confirmed. Most experienced some form of social stress or strain prior to or during the time that they were in the militia, and most conditions for social movement development as specified by Smelser were met and confirmed by the data.     

Kostenstruktur und Ästhetisierung?

Life style research has become an independent branch of social structure analysis, that systematically complements classical research on social inequality in the explanation of social action and of attitudes. However, there are important theoretical gaps in life style research: firstly, there is a lack of theoretical proposals to explain the statistical connection between life styles on the one hand and social action and attitudes on the other hand. Secondly, it remains unclear, why life styles sometimes are very good predictors of social action and at other times they are not. In a first step this article puts forward an action theoretic framework as foundation for life style research, that implies a conceptual shift from life styles to cultural preferences. In a second step I develop three theses, that state relatively precisely the conditions for a high or low explanatory power of cultural preferences. They are empirically tested in a secondary data analysis, that supports the applicability of the theoretical ideas developed in the paper.     

The failure of meta-analytic asymptotics for the seemingly efficient estimator of the common risk difference

We consider the case of a multicenter trial in which the center specific sample sizes are potentially small. Under homogeneity, the conventional procedure is to pool information using a weighted estimator where the weights used are inverse estimated center-specific variances. Whereas this procedure is efficient for conventional asymptotics (e. g. center-specific sample sizes become large, number of center fixed), it is commonly believed that the efficiency of this estimator holds true also for meta-analytic asymptotics (e.g. center-specific sample size bounded, potentially small, and number of centers large). In this contribution we demonstrate that this estimator fails to be efficient. In fact, it shows a persistent bias with increasing number of centers showing that it isnot meta-consistent. In addition, we show that the Cochran and Mantel-Haenszel weighted estimators are meta-consistent and, in more generality, provide conditions on the weights such that the associated weighted estimator is meta-consistent.     

Biomechanical aspects of dynamic stability

Walking is a fundamental motor skill that significantly affects the level of independence in older adults. The amount of variability present in a walking pattern reflects the quality of neuromuscular control. It is well established that a large proportion of falls in older people occurs when walking. The prevention of falls is vital for minimizing disability, preventing injury, and impeding the development of frailty and subsequent deterioration in quality of life. The present literature review focuses on dynamic stability. In dynamic stability, both the base of support and the center of mass are in motion, and effective balance function is required. In general, older adults are expected to have different movement patterns from younger adults, expressed by differences in limb kinematics and kinetics. A better understanding of the biomechanical variables involved can help anticipate and prevent potential falls.     

Modelling the effects of repellent chemicals on foraging bees

Summary.  Many pesticide sprays that are used for crop protection are harmful to honey-bees. It can therefore be beneficial to add to the spray chemical compounds that are repellent to bees, to discourage them from feeding on recently sprayed crops. Experiments were conducted using an artificial feeding station to assess the repellent effects of various compounds. In this system, bees arrive at the feeding station, choose between feeding dishes to which different chemicals have been added, feed for a variable period and then depart. The number of bees at each feeding dish is recorded at intervals of 1 min. We discuss the analysis of data from this type of experiment, based on a queuing theory model.