Spatial structure in a shift-share decomposition: new results for the Italian industrial districts case

In a previous work, a spatial shift-share model was proposed. That model took into account both the activity information of the territory and the legal status of the enterprises working inside it. The model presented, which had a twofold form, developed and came together into a unique formulation. The present proposal is able to suitably catch the neighborhood’s effect on the variation of an economical variable measured on the examined territory. This paper does not intend to repropose the aspects regarding the theoretical evolution of the first model. Instead, the principal goal is to make a comparison ceteris paribus between the results obtained with the new model and those reached through the application of the previous one, so to highlight the role of the association between the two factors included inside the decomposition. Italian industrial districts represent the economical context for this application since each model proposed is applicable to each district case without modifying the theoretical structure which is related, to the neighborhood definition. The application proposed here focuses on data on the chair industrial district located in the border region Friuli Venezia Giulia, with reference to the entire period 2000–2004.     

Exchangeability,predictive sufficiency and Bayesian bootstrap

Summary Let {X _n } be a sequence of random variables conditionally independent and identically distributed given the random variable Θ. The aim of this paper is to show that in many interesting situations the conditional distribution of Θ, given (X ₁,…,X _n ), can be approximated by means of the bootstrap procedure proposed by Efron and applied to a statisticT _n (X ₁,…,X _n ) sufficient for predictive purposes. It will also be shown that, from the predictive point of view, this is consistent with the results obtained following a common Bayesian approach.     

Auditory evoked potentials as a function of sleep deprivation

Event-related brain potentials (ERPs) were studied in subjects deprived of sleep over a 48-h test period to assess the effects of different durations of continuous wakefulness on ERP components and to determine whether changes in the ERP components were related to changes in performance. Forty subjects were randomly assigned to either an experimental (sleep deprived) group (n = 30) or a control (not sleep deprived) group (n = 10). For the experimental subjects, ERP and performance measures were obtained in four-h test blocks throughout the 48-h period. Performance was assessed using the Walter Reed performance assessment battery. The control subjects were tested at the same times except during designated sleep periods. Both performance and evoked potential measures showed systematic changes over the experimental test period in association with sleep deprivation, time of day, and repeated testing. The latency of the N2 component of the evoked potential covaried with throughput measures on the performance assessment battery across the 12 four-h test blocks of the experiment. These data suggest that ERPs reflect central processes that change across the sleep deprivation period and that ERP measures might be useful in assessment and prediction of performance degradation under adverse conditions such as sleep loss.     

The Gini concentration test for survival data

We apply the well known Gini index to the measurement of concentration in survival times within groups of patients, and as a way to compare the distribution of survival times across groups of patients in clinical studies. In particular, we propose an estimator of a restricted version of the index from right censored data. We derive the asymptotic distribution of the resulting Gini statistic, and construct an estimator for its asymptotic variance. We use these results to propose a novel test for differences in the heterogeneity of survival distributions, which may suggest the presence of a differential treatment effect for some groups of patients. We focus in particular on traditional and generalized cure rate models, i.e., mixture models with a distribution of the lifetimes of the cured patients that is either degenerate at infinity or has a density. Results from a simulation study suggest that the Gini index is useful in some situations, and that it should be considered together with existing tests (in particular, the Log-rank, Wilcoxon, and Gray–Tsiatis tests). Use of the test is illustrated on the classic data arising from the Eastern Cooperative Oncology Group melanoma clinical trial E1690.     

A new spatial shift-share decomposition for the regional growth analysis: a local study of the employment based on Italian Business Statistical Register

This paper presents a new shift-share model to decompose the employment growth rate of a territorial unit by taking into consideration the association between industry mix and firm legal status effects measured in its neighborhood. We explicitly consider this kind of association to go beyond the problem of asymmetry found in a previous work. The empirical application refers to the data collected in the Italian Business Statistical Register and, in particular, regional employment figures in Friuli Venezia Giulia (NUTS2 level), for 219 territorial units (LAU2 level) and 12 Local Labour Systems (LLS), for the years 2001 and 2004.     

Maximum likelihood estimation of heterogeneous mixtures of Gaussian and uniform distributions

Existence and consistency of the Maximum Likelihood estimator of the parameters of heterogeneous mixtures of Gaussian and uniform distributions with known number of components are shown under constraints to prevent the likelihood from degeneration and to ensure identifiability. The EM-algorithm is discussed, and for the special case with a single uniform component a practical scheme to find a good local optimum is proposed. The method is compared theoretically and empirically to the estimation of a Gaussian mixture with “noise component” as introduced by Banfield and Raftery (1993) to find out whether it is a worthwhile alternative particularly in situations with outliers and points not belonging to the Gaussian components.     

《凤子》中反讽的各个侧面（下）

在《凤子》中,沈从文破除了归隐的基础、文化预设、物质可能和终极目的,涉及的是归隐的不可能性。沈从文以反讽为特色的隐士的归隐应当被理解为哲学和神秘意义上的归隐。沈从文的所有思考经过了反讽的筛选都被改头换面了,反讽性的超脱,相对于严肃的彻底超脱只是局部的。另外,这是一种双重的超脱：一方面,作者虽不乏公民与政治意识,但这却不成为一种崇拜;另一方面,生命的张力和对知识的相对化阻止了向神秘主义的转变。沈从文的人物并不逃避,他们生活在现实中。从根本上,沈从文将一个以极端化为特色的时代加以相对化。     

Approximating distributions of random functionals of Ferguson-Dirichlet priors

We explore the possibility of approximating the Ferguson-Dirichlet prior and the distributions of its random functionals through the simulation of random probability measures. The proposed procedure is based on the constructive definition illustrated in Sethuraman (1994) in conjunction with the use of a random stopping rule. This allows us to set in advance the closeness to the distributions of interest. The distribution of the stopping rule is derived, and the practicability of the simulating procedure is discussed. Sufficient conditions for convergence of random functionals are provided. The numerical applications provided just sketch the idea of the variety of nonparametric procedures that can be easily and safely implemented in a Bayesian setting.     

Extending the family of Bayesian bootstraps and exchangeable urn schemes

A Bayesian bootstrap for a finite population with censored observations is introduced. It is shown to reduce to the finite population Bayesian bootstrap if there is no censoring and to reduce to the censored data Bayesian bootstrap for a large population. A class of general urn schemes for simulating exchangeable sequences of variables is introduced which is connected to the bootstrap method.     

Influence of urbanization on the avian species-area relationship: insights from the breeding birds of Rome

Urban Ecosystems - The species-area relationship (SAR) is one of the most investigated patterns in ecology and conservation biology, yet there is no study testing how different levels of...