Bayesian updating of atmospheric dispersion after a nuclear accident

Summary.  We consider a Bayesian forecasting system to predict the dispersal of contamination on a large scale grid in the event of an accidental release of radioactivity. The statistical model is built on a physical model for atmospheric dispersion and transport called MATCH. Our spatiotemporal model is a dynamic linear model where the state parameters are the (essentially, deterministic) predictions of MATCH; the distributions of these are updated sequentially in the light of monitoring data. One of the distinguishing features of the model is that the number of these parameters is very large (typically several hundreds of thousands) and we discuss practical issues arising in its implementation as a realtime model. Our procedures have been checked against a variational approach which is used widely in the atmospheric sciences. The results of the model are applied to test data from a tracer experiment.     

Precarity and structural racism in Black youth encounters with police

Youth experience increased surveillance by and involuntary contact with police officers compared with other age groups. Studies that explore the experiences of youth during these encounters are scant and focus on youth with criminal histories. This research aims to explore the experiences of college-attending youth between 18 and 24 years old in two southern states. The study was designed and conducted according to the tenets of interpretative phenomenological analysis (IPA). Twelve Black youth were recruited and interviewed between April 2015 and April 2016. Three superordinate themes (and subthemes) were identified: (1) negative feelings towards the police; (2) precarity of police encounters (subthemes: police as a threat to welfare; it could be me; steps to follow during police encounters; behavior is irrelevant) and; (3) police response is part of structural racism (subthemes: racism is everywhere; media contributes to racism). The importance of these findings for social work practice and research will be discussed.     

Have the relative employment prospects for the low-skilled deteriorated after all?

Has the relative unemployment propensity for the low-skilled increased during the 1990s? We address this question empirically, based on two notions of low skills; i) low education, and ii) low ability, conditioned on education and work experience. Ability is identified by previous earnings. Evaluated by the education-based measure, we find that unemployment propensity has not developed unfavourably for the low-skilled. Evaluated by the ability-based measure, it has. We uncover a steady deterioration of employment prospects for persons with low ability relative to others with similar formal qualifications. The adverse employment effects of being low-skilled are stronger the higher is formal education.All correspondence to Knut Røed. The paper is part of the project Sorting, exposed groups and labour market programs financed by the Research Council of Norway. We wish to thank Rolf Aaberge, Paul Gertler, Harald Goldstein, Karl Ove Moene, Jon Strand, Steinar Strøm, Asbjrn Rødseth and an anonymous referee for helpful comments. Responsible editor: John F. Ermisch.     

Attitudes and Risk Perceptions of Stakeholders in a Nuclear Waste Siting Issue

Stakeholders are often regarded as a critically important group in such issues as the siting of nuclear facilities. In this article, stakeholders were identified on the basis of self-reported activities with regard to a nuclear waste siting issue under debate in four communities. Data were obtained in an extensive mailed survey from a total of 2,548 respondents, approximately an equal number from each community. The overall response rate was 43.9%. Some of the results and telephone interviews with a sample of the nonrespondents indicated that the data are reasonably representative of the respective populations. Stakeholder activities were measured by 20 questions and combined with an index of stakeholder activity level, dichotomized at the 90th percentile. Stakeholders were found to have a higher level of education than others, but otherwise they did not differ in demographics. They did not tend to see risks in general as high, but were quite interested and involved in the nuclear waste siting issue. The stakeholder activity level correlated with risk perception and attitudes in the waste siting issue, but with different signs for those who were for and those who were opposed: stakeholders of both types had more extreme views than others, but in different directions. In addition, stakeholder opponents were much more likely to strongly espouse extreme statements regarding the project than were supporters who also were stakeholders. Implications for risk management and communication are discussed.     

On variable selection in generalized linear and related regression models

This paper is concerned with selection of explanatory variables in generalized linear models (GLM). The class of GLM's is quite large and contains e.g. the ordinary linear regression, the binary logistic regression, the probit model and Poisson regression with linear or log-linear parameter structure. We show that, through an approximation of the log likelihood and a certain data transformation, the variable selection problem in a GLM can be converted into variable selection in an ordinary (unweighted) linear regression model. As a consequence no specific computer software for variable selection in GLM's is needed. Instead, some suitable variable selection program for linear regression can be used. We also present a simulation study which shows that the log likelihood approximation is very good in many practical situations. Finally, we mention briefly possible extensions to regression models outside the class of GLM's.     

Worry and Risk Perception

Risk perception is sometimes measured by means of judgments about worry, sometimes as perceived risk more directly. However, perceived level of risk calls for a more intellectual judgment and worry tends to refer to emotional reactions. These two are therefore not the same and need not be strongly correlated. Results reported here show that perceived risk and worry are indeed weakly correlated, both for generalized worry and for more specific measures of worry matched with the same hazard as risk ratings. A distinction is suggested between cognitive, abstract hazards and concrete, sensory hazards, with implications for the worry-perceived risk relationship. It was furthermore found by means of cluster analysis that there were groups of subject displaying different dynamics of risk and worry.