Unit Root Tests under Time-Varying Variances

The paper provides a general framework for investigating the effects of permanent changes in the variance of the errors of an autoregressive process on unit root tests. Such a framework - which is based on a novel asymptotic theory for integrated and near integrated processes with heteroskedastic errors - allows to evaluate how the variance dynamics affect the size and the power function of unit root tests. Contrary to previous studies, it is shown that non-constant variances can both inflate and deflate the rejection frequency of the commonly used unit root tests, both under the null and under the alternative, with early negative and late positive variance changes having the strongest impact on size and power. It is also shown that shifts smoothed across the sample have smaller impacts than shifts occurring as a single abrupt jump, while periodic variances have a negligible effect even when a small number of cycles take place over a given sample. Finally, it is proved that the locally best invariant (LBI) test of a unit root against level stationarity is robust to heteroskedasticity of any form under the null hypothesis.     

Job Shop Scheduling With Deadlines

In this paper we deal with a variant of the Job ShopScheduling Problem. We consider the addition of release dates anddeadlines to be met by all jobs. The objective is makespanminimization if there are no tardy jobs, and tardiness minimizationotherwise. The problem is approached by using a Shifting Bottleneckstrategy. The presence of deadlines motivates an iterative use of aparticular one machine problem which is solved optimally. Theoverall procedure is heuristic and exhibits a good trade-off betweencomputing time and solution quality.     

Inhabitants' and Experts' Assessments of Environmental Quality for Urban Sustainability

In the context of sustainable urban development, we discuss the assessment of residential environmental quality and the importance of considering inhabitants' perceptions of natural resources in urban areas. Two series of studies, conducted in Guildford (United Kingdom) and in Rome (Italy), addressed the correspondence, or contrast, between inhabitants' and experts' assessment of urban quality concerning two crucial natural resources: air quality and biodiversity. The Guildford study emphasized the accuracy of the assessment of urban air quality by experts and the public. The Rome study focused on the evaluative criteria employed by scientists and the public in assessing the quality of urban green spaces. The results from both studies shed more, albeit complex, light on the simple conventional wisdom about public versus expert understanding and assessment of environmental quality. Study implications are discussed for the support of programs, methods, and tools for urban development, particularly with regard to effective communication and better structuring of residents' participation in urban environmental decision making.     

The management of firms’ alliance network positioning: Implications for innovation

In spite of the frequent calls for a much more integrated approach, the field of management still faces the ever continuing challenges in attempting to bridge the gap between academic research and managerial actions and practices. The field of strategic alliances and firms’ networks are those among which research and practice are more diverging. Trying to cover this separation, the article presents an empirical research on automotive industry that investigates the effects on innovation performance of the position that firms occupy in the network of alliances. The hypothesis that guides this research is that innovation is generated not only from the resources that a company is able to develop internally, but also through access to resources and capabilities owned by the external companies and organizations that the firm itself is tied to through alliances and cooperation agreements. Beyond this broad argument, the paper links tightly research and practice showing way and how the quality of access to resources owned by partners is influenced by the position occupied in the network of alliances and not only by the existence of single collaborative ties. Assuming a managerial approach which relies on the milestones of network research, different types of positioning in the network of alliances are discussed and tested on their impact on innovation.     

Two Strong Families in Southern Europe? Re-Examining the Geography of Kinship Regimes Stemming from the Reciprocity Mechanisms Between Generations

David Reher??s hypothesis of a specific pattern of ??strong family?? characterizing the south of Europe is currently widely shared. Is a further specification possible, one that applies uniquely to the Mediterranean family? The supporting evidence from a large corpus of in-depth interviews of young people aged 30?C34 and living in the north and south of Italy seems to confirm the existence of a dual identity for the strong family, located in two distinct belts within southern Europe divided along a north?Csouth gradient. Pointers to the historical and anthropological roots of this cleavage between the two southern family patterns are sought in two major texts, Ibn Kaldun??s Mouqaddima and Mauss?? ??Essay on the Gift.??     

Minimum Divergence,Generalized Empirical Likelihoods,and Higher Order Expansions

This article studies the minimum divergence (MD) class of estimators for econometric models specified through moment restrictions. We show that MD estimators can be obtained as solutions to a tractable lower dimensional optimization problem. This problem is similar to the one solved by the generalized empirical likelihood estimators of Newey and Smith (2004 Newey , W. K. , Smith , R. J. ( 2004 ). Higher order properties of GMM and Generalized Empirical Likelihood estimators . Econometrica 72 : 219 – 255 .[Crossref], [Web of Science ®] , [Google Scholar]), but it is equivalent to it only for a subclass of divergences. The MD framework provides a coherent testing theory: tests for overidentification and parametric restrictions in this framework can be interpreted as semiparametric versions of Pearson-type goodness of fit tests. The higher order properties of MD estimators are also studied and it is shown that MD estimators that have the same higher order bias as the empirical likelihood (EL) estimator also share the same higher order mean square error and are all higher order efficient. We identify members of the MD class that are not only higher order efficient, but also, unlike the EL estimator, well behaved when the moment restrictions are misspecified.     

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.