A non linear wavelet based estimator for long memory processes

Two wavelet based estimators are considered in this paper for the two parameters that characterize long range dependence processes. The first one is linear and is based on the statistical properties of the coefficients of a discrete wavelet transform of long range dependence processes. The estimator consists in measuring the slope (related to the long memory parameter) and the intercept (related to the variance of the process) of a linear regression after a discrete wavelet transform is performed (Veitch and Abry, 1999). In this paper its properties are reviewed, and analytic evidence is produced that the linear estimator is applicable only when the second parameter is unknown. To overcome this limitation a non linear wavelet based estimator - that takes into account that the intercept depends on the long memory parameter - is proposed here for the cases in which the second parameter is known or the only parameter of interest is the long memory parameter. Under the same hypothesis assumed for the linear estimator, the non linear estimator is shown to be asymptotically more efficient for the long memory parameter. Numerical simulations show that, even for small data sets, the bias is very small and the variance close to optimal. An application to ATM based Internet traffic is presented.Financial support from the Italian Ministry of University and Scientific Research (MIUR), also in the context of the COFIN 2002 ALINWEB (Algorithms for the Internet and the Web) Project, is gratefully acknowledged.     

Modelling the quality of work in the Italian social co-operatives combining NPCA-RSM and SEM-GME approaches

The objective of this paper is to describe and analyse with appropriate statistical models the links between work quality latent factors. Due to the complexity of the task, the analysis is carried out through a two-step approach:

• In the first step, we construct some multidimensional measures of the subjective quality of work, using nonlinear principal component analysis (NPCA) and Rasch analysis with the Rating Scale Model (NPCA-RSM);

• In the second step, we adopt a Structural Equation Model based on generalized maximum entropy (SEM-GME) to integrate the measures achieved with the previous step and to evaluate the relationships between the subjective work quality latent factors.

Therefore, the novel aspects of this paper are the following: (i) The integration between the NPCA-RSM and SEM-GME, which allows reduction of the variables analysed and evaluation of the measurement errors; (ii) The formalization of a Job Satisfaction Model for the study of the relationships between the subjective work quality latent factors in the Italian social services sector.     

A two-phase optimization method for a multiobjective vehicle relocation problem in electric carsharing systems

A spanning subgraph F of a graph G is called an even factor of G if each vertex of F has even degree at least 2 in F. It was conjectured that if a graph G has an even factor, then it has an even factor F with \(|E(F)|\ge {4\over 7}(|E(G)| + 1)+ {2\over 7}|V_2(G)|\), where \(V_2(G)\) is the set of vertices of degree 2 in G. We note that the conjecture is false if G is a triangle. In this paper, we confirm the conjecture for all graphs on at least 4 vertices, and moreover, we prove that if \(|E(H)|\le {4\over 7}(|E(G)| + 1)+ {2\over 7}|V_2(G)|\) for every even factor H of G, then every maximum even factor of G is a 2-factor consisting of even circuits.     

Labour Mobility in Italy: An Empirical Investigation

ABSTRACT: In this paper the author presents a model of unemployment inflows and outflows for the Italian labour market. The flows that the author attempts to estimate are the unemployment inflows and outflows from and to employment. The aggregate estimation suggests that a crucial role is played by the aggregate demand and wage variables, and by the structural change variable. The paper also presents intersectoral estimations of SURE, which take into consideration the flows between Industry and Services. The results are along the lines of those obtained at the aggregate level. An important factor which should be underlined, however, is the asymmetric pattern of the wage variable in the industrial and services sector.     

Female Immigrant Entrepreneurs: More Than a Family Strategy

This article explores the issue of immigrant women entrepreneurship. It focuses on the emergence of new points of view on self‐employed migrant women and in particular their search for independence. With the support of qualitative research carried on in Italy, it will set out a typology of motivations and strategies to become self‐employed in which, besides a “family strategy” and an “independency strategy”, a “mixed network strategy” also emerges. This last focuses on the role of mixed networks (with other foreigners and/or natives) not only in business management but also in the promotion of transnational social activities. Policies that support associations, creating opportunities for gathering and exchanging with local residents and improving the presence of immigrant women in local institutions, could have the side‐effect of increasing participation by immigrant women in self‐employment, not for lack of alternatives but as a path towards self‐fulfilment and empowerment.     

Impact of performance indicators on organisations: a proposal for an evaluation model

This work aims at giving some guidelines to assess the impact of performance indicators on organisations. Performance measurement systems are usually introduced into organisations in order to monitor goal achievement, to allocate resources and to implement a strategy. However, the implementation of performance indicators may generate an alteration in the rational behaviour of the monitored structure. The risk of this impact is always present, and must be considered very carefully in order to preserve the organisation from a counter-productive effect. In the present analytical work, a reference model is proposed as a first step. This model considers all the organisational dimensions on which an indicator may exert its influence. The method makes use of the four Kaplan and Norton’s balanced scorecard perspectives in order to identify the dimensions on which an indicator may exert its impact. Previous works reported in scientific literature do not provide operational models for impact analysis, whereas, the proposed model is linked to an operative procedure in order to support management to make this analysis. The aim is to make the impact analysis less complex by structuring it in a sequence of predefined steps. The proposal is supported by some practical examples.     

Consolidation in the Exchange Industry: What are Exchanges Actually Worth? Some Evidence from a Crises Environment

It is generally acknowledged that the exchange industry shares the typical features of network industries, forcing exchanges to merge across countries. This process was first urged by the need to keep up with technological developments and increased competition from peers and new competitors. Starting 2005 and up to 2007 we observed significant cross border mergers within the securities industry leading to the creation of a few large groups with a diversified business model. It was questioned whether such mergers leaded to a stable equilibrium. Now, in the aftermath of the crisis a new wave of consolidation is taking place. The financial turmoil dramatically affected the market functioning delivering severe strains to the financial sector and modified the way of conducting business. We address the implications of the crisis on exchange??s values, investigating if expectations lying behind values have somewhat changed or compressed or reflect new opportunities.     

The Easterlin paradox and the decline of social capital: An integrated explanation

During the most recent decades people in the US have reported both a stagnant or even declining subjective well-being, as Easterlin (Easterlin, R.A., 1974. Does economic growth improve the human lot? Some empirical evidence. In: David, P.A., Melvin, W.R. (Eds.), Nations and Households in Economic Growth. Academic Press, New York, pp. 89–125) originally observed, and deterioration in their social and family ties, as Putnam (Putnam, R.D. (2000). Bowling Alone. Simon&Schuster, New York) has claimed. The paper proposes an integrated explanation of these two stylised facts by extending the analysis of the relative income explanation of the Easterlin paradox to social relationships as enjoyable ends of choice. Drawing on the evidence-based results of psychology, the paper constructs a model whose premises are (i) that individuals produce social relationships by means of relational ability, (ii) that this ability is primarily shaped during infancy, and (iii) that commercial pressure on children to consume in competition with others may displace the enjoyment of social relationships. The model is thus also able to explain the case of rich countries, like Sweden, that devote relatively more human and material resources than the US to children and adolescents, and that experience both increasing subjective well-being and improving social capital.