Understanding Organized Crime Networks: Evidence Based on Federal Bureau of Narcotics Secret Files on American Mafia

Using unique data on criminal profiles of 800 US Mafia members active in the 50s and 60s and on their connections within the Cosa Nostra network we analyze how the geometry of criminal ties between mobsters depends on family ties, community roots and ties, legal and illegal activities. We contrast our evidence with historical and sociological views about the functioning of the Mafia. Much of our findings are remarkably in line with these views, with interesting qualifications. We interpret some of our results in light of a model of optimal vertical and horizontal connections where more connections mean more profits but also a higher risk of defection. We find that variables that lower the risk of defection, among others, kinship, violence, and mafia culture increase the number of connections. Moreover, there is evidence of strategic endogamy: female children are as valuable as male ones, and being married to a "connected" wife is a strong predictor of leadership within the Mafia ranks. A very parsimonious regression model explains one third of the variability in the criminal ranking of the "men of honor," suggesting that these variables could be used to detect criminal leaders. An additional prediction of our simple model is a right-skewed distribution of the number of connections, which is remarkably in line with the evidence of an extremely hierarchical organization.Mafia; Networks; Intermarriage; Assortative Matching; Crime

Social Network Analysis with sna

Modern social network analysis---the analysis of relational data arising from social systems---is a computationally intensive area of research. Here, we provide an overview of a software package which provides support for a range of network analytic functionality within the R statistical computing environment. General categories of currently supported functionality are described, and brief examples of package syntax and usage are shown.

Residual closeness for helm and sunflower graphs

Vulnerability is an important concept in network analysis related with the ability of the network to avoid intentional attacks or disruption when a failure is produced in some of its components. Often enough, the network is modeled as an undirected and unweighted graph in which vertices represent the processing elements and edges represent the communication channel between them. Different measures for graph vulnerability have been introduced so far to study different aspects of the graph behavior after removal of vertices or links such as connectivity, toughness, scattering number, binding number and integrity. In this paper, we consider residual closeness which is a new characteristic for graph vulnerability. Residual closeness is a more sensitive vulnerability measure than the other measures of vulnerability. We obtain exact values for closeness, vertex residual closeness (VRC) and normalized vertex residual closeness (NVRC) for some wheel related graphs namely helm and sunflower.Publisher's Versio

Postmortem Analysis of Decayed Online Social Communities: Cascade Pattern Analysis and Prediction

Recently, many online social networks, such as MySpace, Orkut, and Friendster, have faced inactivity decay of their members, which contributed to the collapse of these networks. The reasons, mechanics, and prevention mechanisms of such inactivity decay are not fully understood. In this work, we analyze decayed and alive sub-websites from the StackExchange platform. The analysis mainly focuses on the inactivity cascades that occur among the members of these communities. We provide measures to understand the decay process and statistical analysis to extract the patterns that accompany the inactivity decay. Additionally, we predict cascade size and cascade virality using machine learning. The results of this work include a statistically significant difference of the decay patterns between the decayed and the alive sub-websites. These patterns are mainly: cascade size, cascade virality, cascade duration, and cascade similarity. Additionally, the contributed prediction framework showed satisfactory prediction results compared to a baseline predictor. Supported by empirical evidence, the main findings of this work are: (1) the decay process is not governed by only one network measure; it is better described using multiple measures; (2) the expert members of the StackExchange sub-websites were mainly responsible for the activity or inactivity of the StackExchange sub-websites; (3) the Statistics sub-website is going through decay dynamics that may lead to it becoming fully-decayed; and (4) decayed sub-websites were originally less resilient to inactivity decay, unlike the alive sub-websites

Acnowledging for spatial effects in the Portuguese housing markets

The aim of this paper is to revisit a former paper on the Portuguese housing market (1995), acknowledging for spatial effects in order to interpret housing market changes over 1995-2001. The paper will include a first section devoted to explain the differences between the OLS regression analysis and spatial econometrics, explaining the theoretical background used to develop a spatial lag model with the same database; the second section will show the misspecification problems we found when we ran the same model for after 1995-1998 databases; the third section is devoted to describe new housing literature findings relating housing market evolution with the macroeconomic cycles in Portugal; as a consequence the fourth section will include the method we developed with recent census data, to explain the evolution of the country macroeconomic cycles and the agents’ new behavioural attitudes concerning housing; finally and using spatial analysis we can understand the main changes occurred over the 1995-2001 period. The evaluation of the results contradicts some mainstream scholar and political knowledge to explain spatial inequalities between coast and interior municipalities. Complexity issues seem to be present when we consider the way different market agents make decisions on housing markets, looking this good either as a place to live or an alternative investment asset. In the concluding remarks we raise some new interesting questions for further research.

Closeness and Residual Closeness of Harary Graphs

Analysis of a network in terms of vulnerability is one of the most significant problems. Graph theory serves as a valuable tool for solving complex network problems, and there exist numerous graph-theoretic parameters to analyze the system's stability. Among these parameters, the closeness parameter stands out as one of the most commonly used vulnerability metric. Its definition has evolved over time to enhance ease of formulation and applicability to disconnected structures. Furthermore, based on the closeness parameter, residual closeness, which is a newer and more sensitive parameter compared to other existing parameters, has been introduced as a new graph vulnerability index by Dangalchev. In this study, the outcomes of the closeness and residual closeness parameters in Harary Graphs have been examined. Harary Graphs are well-known constructs that are distinguished by having $n$ vertices that are $k$-connected with the least possible number of edges.Comment: 21 pages preprin

'But I thought we were friends?' Life cycles and research relationships

This chapter is concerned with a relatively under-explored aspect of ‘engaged research’ – the nature of friendship relations between researchers and practitioners, and the ethical dilemmas that arise in such relationships. Attention has been paid to the relational aspects of research in the methodology literature, but this chapter focuses more closely on friendship in particular. The chapter is framed around two guiding concerns: how do friendships, formed in and around research, change over time; and in view of friendship conceived in this dynamic fashion, what ethical questions and dilemmas arise for the ‘friends’