Testing constancy of the error covariance matrix in vector models

In this paper a Lagrange multiplier test of the hypothesis that the covariance matrix of a multivariate time series model is constant over time is considered. It is assumed that under the alternative, the error variances are time-varying, whereas the correlations remain constant over time. Under the parameterized alternative hypothesis the variances may change continuously as a function of time or some observable stochastic variables. Small-sample properties of the test statistic are investigated by simulation. The assumption of constant correlations does not appear overly restrictive.     

A stochastic frontier analysis to estimate the relative efficiency of Spanish airports

There exists a common belief among researchers and regional policy makers that the actual central system of Aeropuertos Españoles y Navegación Aérea (AENA) should be changed to one more decentralized where airport managers could have more autonomy. The main objective of this article is to evaluate the efficiency of the Spanish airports using Markov chain Monte Carlo (MCMC) simulation to estimate a stochastic frontier analysis (SFA) model. Our results show the existence of a significant level of inefficiency in airport operations. Additionally, we provide efficient marginal cost estimates for each airport which also cast some doubts about the current pricing practices.     

国际大都市服务业结构与功能特征

在信息技术革命及全球经济服务化的背景下,国际大都市服务业快速发展,服务业内部结构变化及特征出现了新的特点.在分析国际大都市1990-2000年间服务业就业结构变化的基础上,总结出不同层次国际大都市服务业的结构特征;结合国内外相关研究,概括了国际大都市的主要功能特征及未来的发展趋势.     

A comparison of the ratio of variances in distance-based and classical multivariate analysis

In multivariate analysis, the measure of variance accounted for plays a central role. In this paper, we show that an alternative approach, distance-based multivariate analysis, also yields solutions that can be summarized by a ratio of variances. For classical multivariate analysis, this ratio is equal to the variance accounted for (VAF) and in distance-based multivariate analysis it equals distance accounted for (DAF). We show that DAF in distance-based multivariate analysis can always be made higher than VAF in classical multivariate analysis. This property is illustrated for principal components analysis, multiple correspondence analysis, multiple regression, and analysis of variance.     

A bootstrap analysis to investigate the economic efficiency of the logistics industry in Italy*

As argued by literature and consultancy reports, logistics enhances both productivity and competitiveness of several manufacturing supply chains. The analysis of the efficiency trends of logistics providers may shed light on some relevant aspects that can impact on the competitiveness of national industrial systems. Thus, the paper focuses on the Italian logistics supply, shedding lights on the distribution of the efficiency level within the logistics sector and its causes. The analysis is based on a two-stage methodology aimed at estimating the Italian logistics firms’ efficiency and defining some characteristics impacting the efficiency level. At first, we implement a Data Envelopment Analysis model based on balance sheet data, for the period 2006–2012, then an econometric regression is performed in order to identify the effects of main companies’ characteristics on firms’ efficiency. According to our results, size and geographical location are two of the most impacting variables explaining the efficiency score of the Italian logistics providers.