Reinforced urns and the subdistribution beta‐Stacy process prior for competing risks analysis

In this paper, we introduce the subdistribution beta‐Stacy process, a novel Bayesian nonparametric process prior for subdistribution functions useful for the analysis of competing risks data. In particular, we (i) characterize this process from a predictive perspective by means of an urn model with reinforcement, (ii) show that it is conjugate with respect to right‐censored data, and (iii) highlight its relations with other prior processes for competing risks data. Additionally, we consider the subdistribution beta‐Stacy process prior in a nonparametric regression model for competing risks data, which, contrary to most others available in the literature, is not based on the proportional hazards assumption.     

The Dimensions of Agricultural Diversification: A Spatial Analysis of Italian Municipalities

Diversification in agriculture could ensure the survival of farming by broadening the income base of farms and encouraging agricultural sustainability. The diversification of on-farm activities may depend on socioeconomic and environmental characteristics. Although multifunctionality is a hotly debated topic, few papers have focused on the farm characteristics that influence diversification and none have focused on the influence of the spatial pattern. This paper examines the relationship between farm characteristics and the adoption of a specific type of diversification. An econometric model is presented that uses a spatial autoregressive lag model at the municipal scale. The results demonstrate that the activation of each diversification dimension is influenced by both internal and external factors, encompassing farmers’ characteristics, the farm structure, and territorial features, including regional and spatial patterns. Deepening is mainly influenced by the farmer’s age, education, and the presence of small and labor-intensive farms. The key factors for broadening diversification are the presence of small farms and farms with mixed production (breeding and crop cultivation). Regrounding is most affected by the labor-intensive farms in the area and the farms with mixed production.     

A class of neutral to the right priors induced by superposition of beta processes

A random distribution function on the positive real line which belongs to the class of neutral to the right priors is defined. It corresponds to the superposition of independent beta processes at the cumulative hazard level. The definition is constructive and starts with a discrete time process with random probability masses obtained from suitably defined products of independent beta random variables. The continuous time version is derived as the corresponding infinitesimal weak limit and is described in terms of completely random measures. It takes the interpretation of the survival distribution resulting from independent competing failure times. We discuss prior specification and illustrate posterior inference on a real data example.     

Definitions and linkages between operational and strategic flexibilities

This paper aims at clarifying the concept of strategic flexibility, starting from that much more common of manufacturing flexibility (or operational one). After characterizing the dimensions of the latter, a classification of strategic flexibility is presented which distinguishes four categories. The measures of strategic flexibility are also investigated. Then two analogies are pointed out with the operational flexibility. The first, of the cause-effect type, is on two levels: at the business level, the operational flexibility estimates the variation of practices, while the strategic flexibility measures the effect obtained on performances; at the corporate level, the operational flexibility estimates the variation of competences, while the strategic flexibility evaluates the change in business. The second analogy, related to the classification variables, permits the main types of operational and strategic flexibilities to be placed in a single framework. So this study seeks to provide a framework—which has not been proposed in prior literature—for analyzing and evaluating the correlated concepts of operational and strategic flexibilities, to create a theoretical foundation for future research and empirical testing.     

Winding Stairs: A sampling tool to compute sensitivity indices

Sensitivity analysis aims to ascertain how each model input factor influences the variation in the model output. In performing global sensitivity analysis, we often encounter the problem of selecting the required number of runs in order to estimate the first order and/or the total indices accurately at a reasonable computational cost. The Winding Stairs sampling scheme (Jansen M.J.W., Rossing W.A.H., and Daamen R.A. 1994. In: Gasman J. and van Straten G. (Eds.), Predictability and Nonlinear Modelling in Natural Sciences and Economics. pp. 334–343.) is designed to provide an economic way to compute these indices. The main advantage of it is the multiple use of model evaluations, hence reducing the total number of model evaluations by more than half. The scheme is used in three simulation studies to compare its performance with the classic Sobol' LP. Results suggest that the Jansen Winding Stairs method provides better estimates of the Total Sensitivity Indices at small sample sizes.     

Economic growth,labour flexibilization and employment quality in Colombia, 2002–11

Over the period 2002–11, the Colombian labour market saw a marked improvement in employment opportunities, accompanied by an increase in nonstandard forms of employment. The authors look at how this affected employment quality, using a composite index based on Categorical Principal Components Analysis (CATPCA). They observe a small but widespread improvement in employment quality – mainly for self‐employed women – brought about by higher earnings, increased social protection and less time‐related underemployment. However, a considerable “quality deficit” remains, which calls for policies to strengthen labour market institutions and stimulate productivity and investment.     

Temporary Agency Workers in Italy: Alternative Techniques of Classification

Abstract. Cluster analysis and the classification tree technique are applied to investigate the relationship between the individual characteristics of Italian temporary help agency (THA) workers and their probability of achieving a temporary job. The application aims to show some advantages of these techniques with respect to traditional econometric tools. Sketches of the most common profiles among Italian THA workers are obtained as a result. Besides the typical THA worker pointed out by previous studies (young male workers, with a medium–high level of education, living in the Northern regions), two new profiles have been identified: the first comprising male manual workers with previous job experience, whose average age is over 30 and whose educational level is low; the second comprising young female workers with a medium–high level of education, working in the service sector or in the public sector. The results are compared with the more usual logit analysis and show their robustness.     

The Challenge for the Harmonization of Law

Under globalization and the rapid development of international trade and economic relationships, it is necessary to find common rules in private law. Nonetheless, an aspect that must be taken into account is that law is a mirror of a respective society and therefore it should also be considered that juridical fragmentation reflects these differences among societies. Hence, a ‘glocalized’ approach seems to be more suitable and, for it to be put it into practice, the efforts should be devoted to seeking legal harmonization instead of unification. The former, beside all the other things, is to be preferred in terms of feasibility. Harmonization does not equally show the same degree of difficulty in all the fields: it seems to be easier (and more urgent) to be achieved in obligations-contracts and commercial law than in family law or in property and real rights law. Considering this, our research, contains an overview on the advantages of legal harmonization and a brief survey on methods that have been employed and that are being employed now to reach this goal. Even at this preliminary stage, we have noticed that we should pay attention to a theoretical principles-based logic-systematic method and to the role played by jurists of reaching this goal.     

Objective Bayes Covariate‐Adjusted Sparse Graphical Model Selection

We present an objective Bayes method for covariance selection in Gaussian multivariate regression models having a sparse regression and covariance structure, the latter being Markov with respect to a directed acyclic graph (DAG). Our procedure can be easily complemented with a variable selection step, so that variable and graphical model selection can be performed jointly. In this way, we offer a solution to a problem of growing importance especially in the area of genetical genomics (eQTL analysis). The input of our method is a single default prior, essentially involving no subjective elicitation, while its output is a closed form marginal likelihood for every covariate‐adjusted DAG model, which is constant over each class of Markov equivalent DAGs; our procedure thus naturally encompasses covariate‐adjusted decomposable graphical models. In realistic experimental studies, our method is highly competitive, especially when the number of responses is large relative to the sample size.