Central quantile subspace

Quantile regression (QR) is becoming increasingly popular due to its relevance in many scientific investigations. There is a great amount of work about linear and nonlinear QR models. Specifically, nonparametric estimation of the conditional quantiles received particular attention, due to its model flexibility. However, nonparametric QR techniques are limited in the number of covariates. Dimension reduction offers a solution to this problem by considering low-dimensional smoothing without specifying any parametric or nonparametric regression relation. The existing dimension reduction techniques focus on the entire conditional distribution. We, on the other hand, turn our attention to dimension reduction techniques for conditional quantiles and introduce a new method for reducing the dimension of the predictor $$\mathbf {X}$$. The novelty of this paper is threefold. We start by considering a single index quantile regression model, which assumes that the conditional quantile depends on $$\mathbf {X}$$ through a single linear combination of the predictors, then extend to a multi-index quantile regression model, and finally, generalize the proposed methodology to any statistical functional of the conditional distribution. The performance of the methodology is demonstrated through simulation examples and real data applications. Our results suggest that this method has a good finite sample performance and often outperforms the existing methods.     

Diasporic youth identities of uncertainty and hope: second-generation Albanian experiences of transnational mobility in an era of economic crisis in Greece

This paper explores various dimensions of ‘gender’ and ‘mobility’ among immigrant youth from a transnational perspective in an era of economic crisis. The extent and parameters of continuity, contestation and change in migrant youth identities are analysed and we suggest that neither gender nor identity are stable categories but are embedded in sociocultural particularities both in the country of residence (Greece) but also in the country of origin (Albania). Through in-depth interviews with 52 participants, all second-generation Albanian immigrants in Greece born to two Albanian parents, the paper addresses youth identification in relation to gendered representations of belonging. The narrative accounts that we have selected and analysed reflect the emotional challenges, constraints and creativity of Albanian youth.     

Wage Determination in Post-War Italy

ABSTRACT: A bargaining model is proposed and tested in order to explain the irrelevance of the general labour market conditions to wage settlements in the post-war Italian economy. The model is a “right to manage model”, but the solution cannot be improved, being both on the labour demand curve and on the contract curve. The reason for such an outcome is that both firms and unions have priorities, and distinguish the labour force between insiders and outsiders. Different definitions of insiders are used, but in the postwar Italian economy the employees and ex-employees of the industrial sector appear to be the share of the labour force which have been better protected by both contractual parties.     

Drivers of Change in the Democratic Republic of Congo: The Role of China in Re-Shaping the Country

Africa has always been potentially one of the richest continents in the world, but, due to a series of causes (colonization and decolonization process, wars, dictatorships etc.) it has never reached its full potential. The fight against poverty has been carried out by different institutions at the multilateral and bilateral level during the last 30 years, but the route toward economic development seems to be still long for African countries. This paper will focus on the analysis of the new approach to international cooperation introduced by the People’s Republic of China in order to exchange rights of exploitation of Africa’s mining and natural resources with large amounts of capital without any conditionality. The case-study which will be considered is the agreement concluded between the People’s Republic of China and the Democratic Republic of Congo.     

Analysis of bivariate dichotomous data from a stratified two-stage cluster sample

In the health and social sciences, researchers often encounter categorical data for which complexities come from a nested hierarchy and/or cross-classification for the sampling structure. A common feature of these studies is a non-standard data structure with repeated measurements which may have some degree of clustering. In this paper, methodology is presented for the joint estimation of quantities of interest in the context of a stratified two-stage sample with bivariate dichotomous data. These quantities are the mean value π of an observed dichotomous response for a certain condition or time-point and a set of correlation coefficients for intra-cluster association for each condition or time period and for inter-condition correlation within and among clusters. The methodology uses the cluster means and pairwise joint probability parameters from each cluster. They together provide appropriate information across clusters for the estimation of the correlation coefficients.     

An exploratory study of self-esteem and quality of care of 100 children in foster care

This small-scale research study examined children's perceptions of themselves, their situation, career aspirations and hopes for the future. One hundred San Francisco children in foster care were interviewed and filled out a questionnaire. 50 of the children lived in foster family care; 50 in group homes. The Department of Social Services in San Francisco cooperated in executing this study. Children ranged in ages from 8–18. Both male and female children participated. The questionnaire contained two standarized tests, Coopersmith Self-Esteem Inventory and Parks Career Role Inventory. A section was written by the authors to examine how children in care spend their time, and how they feel about where they live and their foster care status. The last part, an open-ended section asks them which foster care setting they liked best, why, and what they would suggest to improve the foster care system. An additional question “Why do you think you are in foster care?” was designed to elicit the children's understanding of why they lived in foster care rather than their biological home.     

Hierarchical Bayesian modeling of marked non-homogeneous Poisson processes with finite mixtures and inclusion of covariate information

We investigate marked non-homogeneous Poisson processes using finite mixtures of bivariate normal components to model the spatial intensity function. We employ a Bayesian hierarchical framework for estimation of the parameters in the model, and propose an approach for including covariate information in this context. The methodology is exemplified through an application involving modeling of and inference for tornado occurrences.     

Spatial Regression Models Using Inter-Region Distances in a Non-Random Context

This article considers spatial data z( s ₁), z( s ₂),…, z( s _n ) collected at n locations, with the objective of predicting z( s ₀) at another location. The usual method of analysis for this problem is kriging, but here we introduce a new signal-plus-noise model whose essential feature is the identification of hot spots. The signal decays in relation to distance from hot spots. We show that hot spots can be located with high accuracy and that the decay parameter can be estimated accurately. This new model compares well to kriging in simulations.     

Understanding the Relationship Between Direct Experience and Risk Perception of Natural Hazards

Risk perception has been largely examined in studies that have aimed to explain and predict preparedness behavior in the context of natural hazards. Findings from studies on the relationship between previous experience, preparedness, and risk perception in disaster situations have been inconsistent. Hence, the main goal of this work was to explore the influence of physical and emotional experience on risk perception regarding natural hazards. This study was conducted in a statistically representative sample of the city of Iquique, in northern Chile (n = 701), who completed a survey one month after the occurrence of an earthquake and tsunami (8.2 Mw). The survey assessed the experience and preparation actions of survivors in relation to this event. Using a structural equation model, we examined nine proposed relationships, six of which were significant. The final model had an adequate fit (χ² = 752.23, df = 283, comparative fit index [CFI] = 0.90, root mean square error of approximation [RMSEA] = 0.049). Direct experience showed the greatest influence on risk perception: while direct physical experience (i.e., the physical and material consequences associated with the earthquake) maintained a direct positive effect on risk perception, direct emotional experience (i.e., the fear of experiencing an earthquake) produced an indirect positive effect (through worry). Emotional experience, however, did not directly influence current preparedness and risk perception. Implications for understanding the relationship between risk perception and direct experience are discussed.