Objective Bayesian analysis for the multivariate skew-t model

We propose a novel Bayesian analysis of the p-variate skew-t model, providing a new parameterization, a set of non-informative priors and a sampler specifically designed to explore the posterior density of the model parameters. Extensions, such as the multivariate regression model with skewed errors and the stochastic frontiers model, are easily accommodated. A novelty introduced in the paper is given by the extension of the bivariate skew-normal model given in Liseo and Parisi (2013) to a more realistic p-variate skew-t model. We also introduce the R package mvst, which produces a posterior sample for the parameters of a multivariate skew-t model.     

On the estimation of the influence curve

We prove the asymptotic validity of bootstrap confidence bands for the influence curve from its usual estimator (the sensitivity curve). The proof is based on the use of Gill's generalized delta method for Hadamard differentiable operators. Some statistical applications, in particular to the estimation of asymptotic variance, are given.     

Sampling hierarchies of discrete random structures

Statistics and Computing - Hierarchical normalized discrete random measures identify a general class of priors that is suited to flexibly learn how the distribution of a response variable changes...     

Flexible clustering via hidden hierarchical Dirichlet priors

The Bayesian approach to inference stands out for naturally allowing borrowing information across heterogeneous populations, with different samples possibly sharing the same distribution. A popular Bayesian nonparametric model for clustering probability distributions is the nested Dirichlet process, which however has the drawback of grouping distributions in a single cluster when ties are observed across samples. With the goal of achieving a flexible and effective clustering method for both samples and observations, we investigate a nonparametric prior that arises as the composition of two different discrete random structures and derive a closed-form expression for the induced distribution of the random partition, the fundamental tool regulating the clustering behavior of the model. On the one hand, this allows to gain a deeper insight into the theoretical properties of the model and, on the other hand, it yields an MCMC algorithm for evaluating Bayesian inferences of interest. Moreover, we single out limitations of this algorithm when working with more than two populations and, consequently, devise an alternative more efficient sampling scheme, which as a by-product, allows testing homogeneity between different populations. Finally, we perform a comparison with the nested Dirichlet process and provide illustrative examples of both synthetic and real data.     

Population Changes in Europe. Demographic and Social Prospects and Problems

Abstract. Over recent years, the European Community has experienced profound demographic changes which, to a large extent, have already determined its demographic future. One of the more significant consequences of demographic and social trends is a marked fragmentation of the family with people giving absolute priority to the individual dimension in their lives and in terms of society as a whole. Legal regulations and administrative practice have not totally–and not everywhere – adapted to the far-reaching changes in the family so as to adequately protect the family and its weaker members in particular: children, the elderly, the disabled, people with mental and social illnesses, the poor. In this field, some measures will be proposed in this paper. The imbalances in demographic-occupational growth in the Euro-Mediterranean area–the area with which the EC is most directly in contact–are and will be of an exceptional amplitude, as has already been shown, to an extent never before experienced in the history of mankind. We must ask ourselves if this very strong differential pressure, which is also of a political and socio-economic nature, will lead to steady and long-lasting migratory flows. Some considerations regarding the future action and intervention of the EC close the paper.     

Unemployment Duration and Disability: Evidence from Portugal

This paper studies the relationship between having a disability and unemployment duration by focusing on individuals registered at Portuguese job centers. Despite its relevance, because disabled people are likely to occupy disadvantaged positions in the labor market, it has received little attention in the literature. As different disabilities affect unemployment duration differently, we distinguish different types of disabilities and shed light on disability-specific support policies. We apply a discrete time hazard model with unobserved heterogeneity to microdata from the Instituto do Emprego e Formação Profissional, which are free from self-reporting problems in disability identification. We find lower reemployment probabilities for many groups of disabled people: individuals with impairment in general functions, disfiguring, speech and visual disorders, muscle-skeletal and other organ impairments experience the more disadvantaged positions. Decomposition analysis indicates that part of the disadvantage is due to differences in returns rather than to differences in characteristics. These findings suggest that the disadvantage of disabled people in the labor market is not only explained by a different distribution of characteristics but especially by the interaction of their characteristics with the work environment. Policy implications are discussed.     

Arousal and Affective Differences Between Student Gamblers and Non-gamblers during a Card Game

The current study examined the differences in arousal (physiologically and subjectively) between gamblers and non-gamblers. Thirty students from a mid-sized university took part in the study for a chance to win money in a gambling task. Nearly half of the participants identified themselves as non-gamblers and slightly more than half of the participants considered themselves gamblers. Findings indicated that gamblers experienced a significantly higher increase in physiological arousal (heart rate) compared to non-gamblers during the gambling experience. The results suggests the possibility that physiological arousal may play a role in the appeal of gambling to certain types of people. Furthermore, when gamblers suffered a loss at the end of the game, they reported feeling worse as compared to the non-gamblers and relative to their state before playing. Moreover, this affective change explained 28.6% of the variance in gambling behavior according to self-reports. Findings suggest that gamblers in our study may have been more personally invested in the gambling tasks, such that losing was more disappointing to the habitual gamblers than the non-gamblers.