Examination and visualisation of the simplifying assumption for vine copulas in three dimensions

Vine copulas are a highly flexible class of dependence models, which are based on the decomposition of the density into bivariate building blocks. For applications one usually makes the simplifying assumption that copulas of conditional distributions are independent of the variables on which they are conditioned. However this assumption has been criticised for being too restrictive. We examine both simplified and non‐simplified vine copulas in three dimensions and investigate conceptual differences. We show and compare contour surfaces of three‐dimensional vine copula models, which prove to be much more informative than the contour lines of the bivariate marginals. Our investigation shows that non‐simplified vine copulas can exhibit arbitrarily irregular shapes, whereas simplified vine copulas appear to be smooth extrapolations of their bivariate margins to three dimensions. In addition to a variety of constructed examples, we also investigate a three‐dimensional subset of the well‐known uranium data set and visually detect the fact that a non‐simplified vine copula is necessary to capture its complex dependence structure.     

Cohort patterns in adult literacy skills: How are new generations doing?

Skills are core elements of the socio-economic prospects of individuals, while they also improve national productivity, growth and social cohesion. Understanding how skills evolve over time and what drives their evolution has become a policy priority of many European countries. Using the 1994–1998 International Adult Literacy Survey (IALS) and the 2012 Survey on Adult Skills (PIAAC) we build synthetic cohorts and examine how the population gains, loses or preserves cognitive skills (literacy) over time. While, as expected, deterioration in the level of skills due to ageing is common to almost all the European countries studied, for some of them concerns arise for the occurrence of skill deterioration across generations, especially among less well-educated and medium-educated individuals. Certain countries appear to be doing a poorer job in providing the necessary literacy skills over successive generations.     

Joint projections of temperature and precipitation change from multiple climate models: a hierarchical Bayesian approach

Summary.  Posterior distributions for the joint projections of future temperature and precipitation trends and changes are derived by applying a Bayesian hierachical model to a rich data set of simulated climate from general circulation models. The simulations that are analysed here constitute the future projections on which the Intergovernmental Panel on Climate Change based its recent summary report on the future of our planet's climate, albeit without any sophisticated statistical handling of the data. Here we quantify the uncertainty that is represented by the variable results of the various models and their limited ability to represent the observed climate both at global and at regional scales. We do so in a Bayesian framework, by estimating posterior distributions of the climate change signals in terms of trends or differences between future and current periods, and we fully characterize the uncertain nature of a suite of other parameters, like biases, correlation terms and model-specific precisions. Besides presenting our results in terms of posterior distributions of the climate signals, we offer as an alternative representation of the uncertainties in climate change projections the use of the posterior predictive distribution of a new model's projections. The results from our analysis can find straightforward applications in impact studies, which necessitate not only best guesses but also a full representation of the uncertainty in climate change projections. For water resource and crop models, for example, it is vital to use joint projections of temperature and precipitation to represent the characteristics of future climate best, and our statistical analysis delivers just that.     

Social Participation, Sense of Community and Social Well Being: A Study on American, Italian and Iranian University Students

Aim of the study was to assess the relationship between social participation and Sense of Community in a sample of University students and the impact of such variables on Social well being. A further aim was to assess the generality of the relationships between these constructs across different countries, and specifically, the USA, Italy and Iran. The sample includes 200 Italian, 125 American and 214 Iranian University students, male and female. Results show higher levels of social participation, Sense of Community and Social well being among American students. Sense of Community is positively correlated with social participation in all three samples; however, only among Italian students social participation positively predicts Social well being. Implications of results will be discussed.     

Polymorphism-screening: genetic testing for predisposition—guidance for technology assessment

Health policy is increasingly confronted with the demand for financing genetic testing on inherited susceptibility to disease. Tests on polymorphism/SNP associated with multicausal and chronic conditions are already offered in private commercial institutions or in academic hospitals. The increasing pressure on public health services to offer SNP testing leads to first methodological approaches for a generally valid regulatory framework applicable for inclusion or refusal of genetic tests into the public health services. Systematic search in Medline, Embase and the Web for methodological papers or guidelines for the assessment of polymorphism-screening. Since genetic testing has not only clinical and economic effects on health care, but also primarily ethical consequences by profiling our understanding of “health” and “disease”, this paper gives an overview of relevant aspects and background information to consider in the assessment of genetic tests. Although 2–3 million SNPs are identified and the journals are full of reported “significant” associations between disease and mutation, only a few can be replicated unequivocally. The ACCE (Analytic and Clinical Validity, Clinical utility; Ethical, legal and social implications)-framework was developed by the Center of Disease Control for the assessment of genetic testing. This standardised appraisal approach proposes collecting and evaluating: (a) Prevalence, genotype-/phenotype-relation. (b) Clinical presentation: natural history; the different expressions of disease. (c) Performance of the genetic test. (d) Implications for therapy and prevention. (e) Conclusion for clinical applications of risk-profiling of health on their susceptibility to disease and/or for clarification of disease for therapy planning. Since genetic testing is urging its way into the health care system, the actual danger is, that population screening starts before valid evidence from big prospective studies have been carried out and delivered proofs of direct causal associations. Before diffusing into the health care system we are suggesting to take a cautious and standardised approach.     

The professionalization of Spanish social work: moving closer to Europe or away from its roots?

This article will review the processes of professionalization of social work in Spain. With the advent of democratic Spain, many professions began a process of transformation. Those rooted in the relationship between the citizens, their rights and obligations, and the state, were among the first to be challenged. Social work was one of them. Soon thereafter, the European Union (EU), which Spain joined in 1986, brought forth greater challenges and incentives to change. In 1999, Spain and 29 other countries signed the Bologna Declaration, which committed the country to the development of a shared domain (often referred to as ‘espacio común’) with European higher education. This article reviews the historical process of insertion of social work, heavily influenced by the Catholic tradition of caring, into the universities. The paper examines the model of social work education in Spain, before and during Franco's era, and the professionalization (sometimes referred to as ‘tecnificación’) of care-giving and training-paradigms that followed the advent of democracy. Current models and efforts to bring Spanish social work into EU compliance have narrowed the gap with the Anglo-Saxon world; but have they distanced social work in Spain from its roots?     

“Reactive Ethnicity” or “Assimilation”? Statements,Arguments, and First Empirical Evidence for Labor Migrants in Germany

In this article, we scrutinize the often stated assumption that labor migrants in Germany turn away from integration and reaffirm their ethnicity by examining their identificational, cognitive, and social assimilation processes. Using data from the German Socio‐economic Panel, we present trend analyses of different hostland‐ and homeland‐related indicators for the past fifteen years. Results are presented separately for first‐ and second‐generation migrants from Turkey, the EU, and the former Yugoslavia. While not all assimilation‐related indicators change a great deal over time, they show at least a substantial difference between the first and the second generation. With regard to the homeland‐related indicators, the results by no means suggest that Turkish migrants try to compensate for their comparatively disadvantaged social status by revitalizing ethnic cultural habits or homeland‐oriented identifications.     

Identifiability and estimation of recursive max‐linear models

We address the identifiability and estimation of recursive max‐linear structural equation models represented by an edge‐weighted directed acyclic graph (DAG). Such models are generally unidentifiable and we identify the whole class of DAG s and edge weights corresponding to a given observational distribution. For estimation, standard likelihood theory cannot be applied because the corresponding families of distributions are not dominated. Given the underlying DAG, we present an estimator for the class of edge weights and show that it can be considered a generalized maximum likelihood estimator. In addition, we develop a simple method for identifying the structure of the DAG. With probability tending to one at an exponential rate with the number of observations, this method correctly identifies the class of DAGs and, similarly, exactly identifies the possible edge weights.