1,720,966 research outputs found
Cost efficiency, asymmetry and dependence in US electricity industry
No full textWe propose an empirical application of models derived in Bonanno et al. (2017) for estimating cost efficiency (CE) on data used by Greene (1990) to test Gamma distribution for the inefficiency component and by Smith (2008) to test the dependence between the two error terms of a Stochastic Frontier (SF). We also derive the closed-form of denisty function of the overall error term and the formula to calculate the Cost Efficiency (CE) scores
The ‘wrong skewness’ problem: a re-specification of stochastic frontiers
Get PDFIn this paper, we study the ‘wrong skewness phenomenon’ in stochastic frontiers (SF), which consists in the observed difference between the expected and estimated sign of the asymmetry of the composite error, and causes the ‘wrong skewness problem’, for which the estimated inefficiency in the whole industry is zero. We propose a more general and flexible specification of the SF model, introducing dependences between the two error components and asymmetry (positive or negative) of the random error. This re-specification allows us to decompose the third moment of the composite error into three components, namely: (i) the asymmetry of the inefficiency term; (ii) the asymmetry of the random error; and (iii) the structure of dependence between the error components. This decomposition suggests that the wrong skewness anomaly is an ill-posed problem, because we cannot establish ex ante the expected sign of the asymmetry of the composite error. We report a relevant special case that allows us to estimate the three components of the asymmetry of the composite error and, consequently, to interpret the estimated sign. We present two empirical applications. In the first dataset, where the classic SF has the wrong skewness, an estimation of our model rejects the dependence hypothesis, but accepts the asymmetry of the random error, thus justifying the sign of the skewness of the composite error. More importantly, we estimate a non-zero inefficiency, thus solving the wrong skewness problem. In the second dataset, where the classic SF does not yield any anomaly, an estimation of our model provides evidence for the presence of dependence. In such situations, we show that there is a remarkable difference in the efficiency distribution between the classic SF and our class of models. © 2017, Springer Science+Business Media New York
On the extreme hydrologic events determinants by means of Beta-Singh-Maddala reparameterization
Get PDFIn previous studies, beta-k distribution and distribution functions strongly related to that, have played important roles in representing extreme events. Among these distributions, the Beta-Singh-Maddala turned out to be adequate for modelling hydrological extreme events. Starting from this distribution, the aim of the paper is to express the model as a function of indexes of hydrological interest and simultaneously investigate on their dependence with a set of explanatory variables in such a way to explore on possible determinants of extreme hydrologic events. Finally, an application to a real hydrologic dataset is considered in order to show the potentiality of the proposed model in describing data and in understanding effects of covariates on frequently adopted hydrological indicators
Demographic, genetic and phenotypic characteristics of centenarians in Italy: Focus on gender differences
No full textAn impressive and coherent series of epidemiological data from different populations (New England Americans, Mormons, Ashkenazi Jewish, Icelandic, Okinawan Japanese, Italians) suggests that long-lived subjects able to reach the extreme limits of human life, such as centenarians and supercentenarians, represent an extraordinary and informative model to identify the mechanisms responsible for healthy aging and human longevity. In most studies, genetic, demographic and phenotypic characteristics of longevity are discussed separately. However, longevity is a very complex trait due to the complicated interactions of numerous genetic and environmental factors. It is therefore necessary to analyse centenarians with a multidimensional approach, trying to consider different aspects simultaneously. In this review we will focus on Italian centenarians, who have been extensively studied for many years with different approaches, in order to show their peculiarities and the emerging data from the studies carried out on this exceptional population
L'impatto del consolidamento del sistema bancario italiano sull'efficienza di costo: frontiere stocastiche, dipendenza tra gli errori e copule
No full textDottorato in Scienze economiche e aziendali, XXV ciclo. A.a. 2009-201
Associazione ed efficienza nei modelli logit-multivariati
No full textThe goal of this work is to investigate the role that the association, among categorical variables, plays in estimating of the so-called marginal parameters of a Multivariate Logit Models. By comparing, in terms of asymptotic efficiency, the maximum likelihood estimators of the vector of the marginal parameters to the one obtained under the wrong hypothesis of stochastic independence (misspecification), we provide the general conditions of equality among asymptotic variance matrices of the two alternative estimators. Furthermore, by analyzing the particular case of bivariate binary variables with constraints of homogeneity (between, within and complete) on the marginal probabilities, we show that there are situations in which the gain of efficiency of the maximum likelihood estimator with respect to that of misspecification grows when the association among variables increases too
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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