0000000001011232
AUTHOR
Stefania Vitali
showing 11 related works from this author
Multi-scale analysis of the European airspace using network community detection
2014
We show that the European airspace can be represented as a multi-scale traffic network whose nodes are airports, sectors, or navigation points and links are defined and weighted according to the traffic of flights between the nodes. By using a unique database of the air traffic in the European airspace, we investigate the architecture of these networks with a special emphasis on their community structure. We propose that unsupervised network community detection algorithms can be used to monitor the current use of the airspaces and improve it by guiding the design of new ones. Specifically, we compare the performance of three community detection algorithms, also by using a null model which t…
Where Has All the Trading Gone? A Network Approach to European Stock Exchanges and Alternative Trading Venue
2011
This paper investigates the network features of European trading venues by analyzing the behavior of simultaneously quoted stock. Equity trading venues include both regulated Stock Exchanges (SEs) and Alternative Trading Venues (ATVs) and these represent the nodes of our network. The connections among these nodes are determined by choices of investors to exploit various venues in which a stock may be traded. Using trading volume data of nearly 22,000 equities we use social network analysis to measure prestige and connectivity between the various trading venues between 2005 and 2009. We find that the evolution of ATVs (including multi-lateral trading venues BATS, Chi-X and Turquoise, as well…
The Dynamic of Innovation Networks: A Switching Model on Technological Change
2012
In this paper we introduce an agent-based model with heterogeneous firms which compare their mutual innovation strategies on different network structures. By implementing a dynamic behavioral switching via a fitness mechanism based on agents performance, companies can endogenously modify their tactics of technological change and switch among three groups: stand-alone innovators, collaborative innovators and imitators. We focus the analysis on the impact of these three innovation categories on micro, meso and macro aggregates. Our findings show that collaborative companies are those having the highest positive impact on the economic system. Moreover, we study the properties of the emerging n…
The Community Structure of the Global Corporate Network
2013
We investigate the community structure of the global ownership network of transnational corporations. We find a pronounced organization in communities that cannot be explained by randomness. Despite the global character of this network, communities reflect first of all the geographical location of firms, while the industrial sector plays only a marginal role. We also analyze the network in which the nodes are the communities and the links are obtained by aggregating the links among firms belonging to pairs of communities. We analyze the network centrality of the top 50 communities and we provide the first quantitative assessment of the financial sector role in connecting the global economy.
Financial Fragility and Distress Propagation in a Network of Regions
2012
Building on previous works on business fluctuations, we model the propagation of financial distress in a network of regions, each populated by heterogeneous interacting firms and banks. In order to diversify risk, firm sell goods outside their own region and borrow from banks located there. However, this results in ties across regions which propagate financial distress across regional borders. We investigate how the average level of economic integration affects the probability of both individual and systemic failures. We find that the benefit of greater diversification is eventually offset by the effect of financial acceleration and contagion. In particular, beyond a certain level of integr…
Geography versus topology in the European Ownership Network
2011
In this paper, we investigate the network of ownership relationships among European firms and its embedding in the geographical space. We carry out a detailed analysis of geographical distances between pairs of nodes, connected by edges or by shortest paths of varying length. In particular, we study the relation between geographical distance and network distance in comparison with a random spatial network model. While the distribution of geographical distance can be fairly well reproduced, important deviations appear in the network distance and in the size of the largest strongly connected component. Our results show that geographical factors allow us to capture several features of the netw…
The network of global corporate control.
2011
The structure of the control network of transnational corporations affects global market competition and financial stability. So far, only small national samples were studied and there was no appropriate methodology to assess control globally. We present the first investigation of the architecture of the international ownership network, along with the computation of the control held by each global player. We find that transnational corporations form a giant bow-tie structure and that a large portion of control flows to a small tightly-knit core of financial institutions. This core can be seen as an economic “super-entity” that raises new important issues both for researchers and policy make…
Spatial Localization in Manufacturing: A Cross-Country Analysis
2009
This paper employs a homogenous firms' database to investigate industry localiza- tion in European countries. More specifically, we compare, across industries and countries, the predictions of two of the most popular localization indices, i.e., the Ellison and Glaeser index (Ellison and Glaeser, 1997) and the Duranton and Over- man index (Duranton and Overman, 2005). We find that, independently from the index used, localization is a pervasive phenomenon in all countries studied, but the degree of localization is very uneven across industries in each country. Furthermore, we find that the two indices significantly diverge in predicting the intensity of the forces generating localization with…
Exploratory analysis of safety data and their interrelation with flight trajectories and network metrics
2013
This paper presents an exploratory analysis of the correlation between different network metrics and safety events. The objective is to develop analysis methods and indicators that relate the network structure with safety events. In particular by using data gathered with an automatic tool developed by EUROCONTROL and a database of traffic data, we measured the correlations between the classical metrics of the airspace network, especially the network of navigation points, and the occurrence of Short Term Conflicts Alerts (STCA). The results obtained are not univocal; correlation between STCA occurrences and classical network metrics are present but the correlation coefficient is around 0.7. …
The impact of classes of innovators on Technology, Financial Fragility and Economic Growth
2011
In this paper, we study innovation processes and technological change in an agent-based model. By including a behavioral switching among heterogeneous innovative firms, which can endogenously change among three different classes (single innovators, collaborative innovators and imitators) on the base of their R&D expenditures, the model is able to replicate, via simulations, well known industrial dynamic and growth type stylized facts. Moreover, we focus the analysis on the impact of these three innovation categories on micro, meso and macro aggregates. We find that collaborative companies are those having the highest positive impact on the economic system. The model is then used to study th…
The community structure of the global corporate network.
2013
We investigate the community structure of the global ownership network of transnational corporations. We find a pronounced organization in communities that cannot be explained by randomness. Despite the global character of this network, communities reflect first of all the geographical location of firms, while the industrial sector plays only a marginal role. We also analyze the network in which the nodes are the communities and the links are obtained by aggregating the links among firms belonging to pairs of communities. We analyze the network centrality of the top 50 communities and we provide the first quantitative assessment of the financial sector role in connecting the global economy.