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We develop a model in which connections between individuals serve as social collateral to enforce informal insurance payments. We show that: (i) The degree of insurance is governed by the expansiveness of the network, measured with the per capita number of connections that groups have with the rest of the community. "Two-dimensional" networks—like real-world networks in Peruvian villages—are sufficiently expansive to allow very good risk-sharing. (ii) In second-best arrangements, insurance is local: agents fully share shocks within, but imperfectly between endogenously emerging risk-sharing groups. We also discuss how endogenous social collateral affects our results. (JEL D85, G22, O15, O17, Z13)

AbstractWe present a new index for measuring income inequality in networks. The index is based on income comparisons made by the members of a network who are linked with each other by direct social connections. To model the comparisons, we compose a measure of relative deprivation for networks. We base our new index on this measure. The index takes the form of a ratio: the network's aggregate level of relative deprivation divided by the aggregate level of the relative deprivation of a hypothetical network in which one member of the network receives all the income, and it is with this member that the other members of the network compare their incomes. We discuss the merits of this representation. We inquire how changes in the composition of a network affect the index. In addition, we show how the index accommodates specific network characteristics.

Social networking applications such as Facebook, Twitter, and Crowdrise offer new ways for nonprofits to engage the community in fundraising efforts. This study employs data from Facebook Causes to examine the nature and determinants of charitable giving in social networking environments. Our findings suggest donations on these sites are not driven by the same factors as in "off-line" settings. Instead, a social network effect takes precedence over traditional economic explanations. Facebook donors do not seem to care about efficiency ratios, their donations are typically small, and fundraising success is related not to the organization's financial capacity but to its "Web capacity." Moreover, online donors are prone to contribute to certain categories of causes more than others, especially those related to health. Given the growth in social media-driven fundraising—and the increase in crowdfunding, slacktivism, impulse donating, and other new practices this entails—these findings carry notable theoretical and practical implications.

Varios estudios demuestran que la corrupción no es únicamente un problema de negociación en el que un agente busca un objetivo en particular y un oficial exige un soborno para realizar su trabajo. Otras líneas de investigación analizan como las estructuras sociales pueden originar una sociedad corrupta. En este trabajo, combino la aproximación individualista de la teoría económica con el enfoque más social de otras ciencias sociales como la sociología, las ciencias políticas y la administración de empresas. Esto me permite estudiar la corrupción y el papel de las agencias de monitoreo cuando los actos corruptos se desarrollan bajo una estructura de redes sociales. El objetivo es comprobar que si la red es completa (i.e. no exhibe ninguna brecha), la coordinación entre agentes es más fluída y es más sencillo alcanzar objetivos corruptos. Además, cuando se incluye a las agencias de monitoreo, es fundamental que las instituciones y estas agencias complementen sus labores para prevenir el acto de corrupción de una manera más efectiva. Para ello, combino dos teorías sobre el comportamiento humano: la teoría de redes sociales y la teoría de juegos. Después de estudiar cuatro posibles escenarios, dos sin incluir las agencias de monitoreo y dos incluyéndolas, demuestro que la hipótesis planteada no puede ser descartada. Inclusive, si la penalidad que castiga el comportamiento corrupto es baja (o el costo administrativo de la justicia es alto) entonces los agentes preferirán involucrarse en actividades corruptas, sobre todo cuando la red es completa. Por el contrario, si la honestidad es altamente recompensada, los agentes tienen incentivos suficientes para no aceptar propuestas corruptas. La existencia de agencias de monitoreo, representadas como medios de comunicación libres, pueden desmotivar la corrupción desde el inicio. ; Many studies show that corruption is not only a bargaining problem between an agent that has an specific objective and an official that demand a bribe to do her job. Other lines of research analyzes how social structures are the origin of a corrupt society. In this work I combine the individualistic approach of economic theory with the social view of other social sciences such as sociology, political sciences and business administration to study corruption and the role of monitoring agencies when corruption takes place in a network structure. I will try to prove that if the social network is complete (i.e. it exhibits no gaps) then the coordination among agents is more fluent and it is easier to achieve corrupt objectives. On the other hand, institutions can generate incentives even if the network is complete. When monitoring agencies are included, it is important for institutions and monitoring agencies to complement each other to prevent more effectively the act of corruption. For this, I combine two theories on human behavior: social network theory and game theory. After studying four possible settings, two without monitoring agencies and two including them, I find that the hypothesis cannot be ruled out. Moreover, if the penalty for corrupt behavior is low (or the administrative cost of justice is high) then agents will prefer to get involved in corrupt activities, specially if the network is complete. On the other hand, if honesty is highly rewarded, agents have enough incentives to reject corrupt proposals. The existence of monitoring agencies represented as free press can discourage corruption from the beginning.

Comprendre le séquençage dans les communications dans un réseau social :Le séquençage est un processus décisionnel indispensable dans la circulation de l'information. Cette note de recherche propose la conceptualisation de séquençage pour comprendre comment et pourquoi les expéditeurs d'information « priorisent » certains membres du réseau pendant qu'ils communiquent avec d'autres. Nous examinons l'utilité de cette conceptualisation avec les données recueillies à partir de GRAND, un réseau académique. Le concept de séquençage permet aux chercheurs d'explorer les processus décisionnels qui surviennent avant le flux d'information et de lier le comportement des individus au contexte social. Sequencing is an indispensable decision-making process during information flows. This paper proposes the conceptualization of sequencing to understand how and why information senders prioritize some network members when they communicate with others. We examine the usefulness of this conceptualization with data collected from GRAND, a scholarly network. The concept of sequencing enables researchers to explore the decision-making process that occurs prior to information flows and link individuals'behavior to the social context.

This paper reports on an evaluation undertaken of the potential impact of a Network for Educators: the Pathways for Learning, Anywhere, Anytime (PLANE) website. The evaluation was undertaken in New South Wales, Australia with teachers in Government, Catholic and Independent schools in both rural and suburban areas. The benefits and challenges associated with supporting teachers' information and communication technologies (ICT) skills via a professional learning network platform are highlighted. Results of the study indicate that a well-designed online platform could potentially provide a space for teachers to learn to integrate ICT in their teaching with and from each other within a learning community.

Background: Online social networking might facilitate the establishment of social contacts for people with psychosis, who are often socially isolated by the symptoms and consequences of their disorder. Aims: We carried out a systematic review exploring available evidence on the use of online social networking in people with psychosis. Methods: The review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Included studies examined the use of the online social networking by people with an a priori diagnosis of psychosis (inclusive of bipolar disorder). Data from included studies were extracted and narratively synthesised. Results: A total of 11 studies, published between 2005 and 2013, reported data on online social networking in people with psychosis. People with psychosis seem to spend more time in chat rooms or playing online games than control groups. The use of other online tools, such as Facebook or communication through e-mail, is lower or the same than controls. Online social networking was used by patients with psychosis for establishing new relationships, maintaining relationships/reconnecting with people and online peer support. Conclusion: Online social networking, in the form of forums or online chats, could play a role in strategies aimed at enhancing social networks and reduce the risk of isolation in this population.

This was the first textbook on social network analysis integrating theory, applications, and professional software for performing network analysis (Pajek). Step by step, the book introduces the main structural concepts and their applications in social research with exercises to test the understanding. An application section explaining how to perform the network analyses with Pajek software follows each theoretical section. Pajek software and datasets for all examples are freely available, so the reader can learn network analysis by doing it. In addition, each chapter offers case studies for practising network analysis. In the end, the reader has the knowledge, skills, and tools to apply social network analysis in all social sciences, ranging from anthropology and sociology to business administration and history

Using a dataset of over 1.9 million messages posted on Twitter by about 25,000 ISIS sympathizers, we explore how ISIS makes use of social media to spread its propaganda and recruit militants from the Arab world and across the globe. By distinguishing between violence-driven, theological, and sectarian content, we trace the connection between online rhetoric and key events on the ground. To the best of our knowledge, ours is one of the first studies to focus on Arabic content, while most literature focuses on English content. Our findings yield new important insights about how social media is used by radical militant groups to target the Arab-speaking world, and reveal important patterns in their propaganda efforts.

AbstractThe application of social network analysis methodologies is relatively new for mainstream evaluation and has yet to be fully explored in this discipline. This chapter discusses how and why SNA is appropriate for evaluation practice.

'The economic importance of social interactions not mediated by the market has long been recognized. However, it is only the emergence of network analysis that has supplied a useful method of study. The editors have performed a signal service by their anthology of important articles. They have covered all the major studies and represented well the rapid emergence of a new and important field, to which they have been among the most significant contributors.'--Kenneth Arrow, Stanford University, US. This comprehensive two-volume set brings together important contributions providing fundamental economic analyses of social networks and the central roles they play in many facets of our lives. The first volume consists of classic articles that model network formation and games on networks, as well as those on the identification of peer effects from an econometric viewpoint. The second volume provides empirical analyses of network effects on labor, education, development, crime and industrial organization, as well as some laboratory and field experiments. This set of indispensable papers, with an original introduction by the editors, will prove an essential tool to researchers, scholars and practitioners involved in this field