Benefits of Friendship
Josh Lerner & Ulrike Malmendier
NBER Working Paper, March 2011
Abstract:
To what extent do peers affect our occupational choices? This question has been of particular interest in the context of entrepreneurship and policies to create a favorable environment for entry. Such influences, however, are hard to identify empirically. We exploit the assignment of students into business school sections that have varying numbers of classmates with prior entrepreneurial experience. We find that the presence of entrepreneurial peers strongly predicts subsequent entrepreneurship rates of students without an entrepreneurial background, but in a more complex way than the literature has previously suggested: A higher share of entrepreneurial peers leads to lower rather than higher subsequent rates of entrepreneurship. However, the decrease in entrepreneurship is entirely driven by a significant reduction in unsuccessful entrepreneurial ventures. The effect on the rate of successful post-MBA entrepreneurs, instead, is insignificantly positive. In addition, sections with few prior entrepreneurs have a considerably higher variance in their rates of unsuccessful entrepreneurs. The results are consistent with intra-section learning, where the close ties between section-mates lead to insights about the merits of business plans.
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Dormant Ties: The Value Of Reconnecting
Daniel Levin, Jorge Walter & Keith Murnighan
Organization Science, forthcoming
Abstract:
The social networks literature suggests that ties must be maintained to retain value. In contrast, we show that reconnecting dormant ties - former ties, now out of touch - can be extremely useful. Our research prompted Executive MBA students to consult their dormant contacts about an important work project; outcomes compared favorably to those of their current ties. In addition, reconnecting previously strong ties led to all of the four benefits that are usually associated with either weak ties (efficiency and novelty) or strong ties (trust and shared perspective). These findings suggest that dormant relationships - often overlooked or underutilized - can be a valuable source of knowledge and social capital.
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Geographic Constraints on Social Network Groups
Jukka-Pekka Onnela et al.
PLoS ONE, April 2011, e16939
Abstract:
Social groups are fundamental building blocks of human societies. While our social interactions have always been constrained by geography, it has been impossible, due to practical difficulties, to evaluate the nature of this restriction on social group structure. We construct a social network of individuals whose most frequent geographical locations are also known. We also classify the individuals into groups according to a community detection algorithm. We study the variation of geographical span for social groups of varying sizes, and explore the relationship between topological positions and geographic positions of their members. We find that small social groups are geographically very tight, but become much more clumped when the group size exceeds about 30 members. Also, we find no correlation between the topological positions and geographic positions of individuals within network communities. These results suggest that spreading processes face distinct structural and spatial constraints.
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It is not Just the Economy: Declining Migration and the Rise of Secular Rootedness
Thomas Cooke
Population, Space and Place, May-June 2011, Pages 193-203
Abstract:
Americans have always been viewed, both by themselves and by others, as a migrant society. However, migration rates have reached record lows: only 1.6% of Americans moved from one state to another in 2009, and only 3.7% moved from one county to another. This research conducts a decomposition of the change in migration rates between 1999 and 2009 using data from the Current Population Survey. The analysis concludes that about 63% of the decline in migration rates between 1999 and 2009 can be attributed to the direct effects of the economic crisis that began in 2007, and another 17% of the decline can be attributed to demographic changes (e.g. the aging of the population) but that the remaining 20% of the decrease in migration is due to a decline in migration behaviour, or increased rootedness, that applies to all demographic categories. The discussion focuses on the implications of the universal, or secular, rise in rootedness for migration studies.
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Information Shocks and Social Networks
David Figlio, Sarah Hamersma & Jeffrey Roth
NBER Working Paper, April 2011
Abstract:
The relationships between social networks and economic behavior have been well-documented. However, it is often difficult to distinguish between the role of information sharing and other features of a neighborhood, such as factors that are common to people of the same ethnicities or socio-economic opportunities, or uniquely local methods of program implementation. We seek to gain new insight into the potential role of information flows in networks by investigating what happens when information is disrupted. We exploit rich microdata from Florida vital records and program participation files to explore the effects of neighborhood social networks on the degree to which immigrant WIC participation during pregnancy declined in the "information shock" period surrounding welfare reform. We compare changes in WIC participation amongst Hispanic immigrants living in neighborhoods with a larger concentration of immigrants from their country of origin to those with a smaller concentration of immigrants from their country of origin, holding constant the size of the immigrant population and the share of immigrants in the neighborhood who are Hispanic. We find strong evidence to support the notion that social networks mediated the information shock faced by immigrant women in the wake of welfare reform.
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Sandeep Khot, Buhm Soon Park & W.T. Longstreth
Academic Medicine, April 2011, Pages 502-508
Purpose: From the outbreak of the Korean War in 1950 through the end of the Vietnam War in 1973, many American physicians were inducted into military service through the Doctor Draft. Some fulfilled their obligations by conducting clinical research in the National Institutes of Health (NIH) Associate Training Program (ATP) and later labeled themselves "Yellow Berets." The authors examined the history of the ATP and its influence on NIH associates' future careers.
Method: Via interviews with former associates and archival research, the authors explored the training and collaboration in the ATP during 1953-1973. Using databases, they compared later academic positions of associates with those of nonassociate peers who also entered academia and identified associates with prestigious awards or honorary society memberships.
Results: The physician-scientists trained in the selective ATP were highly qualified individuals who received training and networking opportunities not available to others. They were approximately 1.5 times as likely as nonassociates to become a full professor, twice as likely to become chair of a department, and three times as likely to become a dean. Associates were also more likely to hold positions at top-ranked medical schools, to fill leadership roles in the NIH, and to win prestigious awards and honorary society memberships.
Conclusions: The cadre of physician-scientists trained in the ATP during the Doctor Draft rose through the academic ranks to leadership roles and continued their productive scientific collaborations. Their legacy continues to have implications for medical research today, particularly for training programs in clinical research.
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A Social Network Analysis of Treatment Discoveries in Cancer
Athanasios Tsalatsanis et al.
PLoS ONE, March 2011, e18060
Abstract:
Controlled clinical trials are widely considered to be the vehicle to treatment discovery in cancer that leads to significant improvements in health outcomes including an increase in life expectancy. We have previously shown that the pattern of therapeutic discovery in randomized controlled trials (RCTs) can be described by a power law distribution. However, the mechanism generating this pattern is unknown. Here, we propose an explanation in terms of the social relations between researchers in RCTs. We use social network analysis to study the impact of interactions between RCTs on treatment success. Our dataset consists of 280 phase III RCTs conducted by the NCI from 1955 to 2006. The RCT networks are formed through trial interactions formed i) at random, ii) based on common characteristics, or iii) based on treatment success. We analyze treatment success in terms of survival hazard ratio as a function of the network structures. Our results show that the discovery process displays power law if there are preferential interactions between trials that may stem from researchers' tendency to interact selectively with established and successful peers. Furthermore, the RCT networks are "small worlds": trials are connected through a small number of ties, yet there is much clustering among subsets of trials. We also find that treatment success (improved survival) is proportional to the network centrality measures of closeness and betweenness. Negative correlation exists between survival and the extent to which trials operate within a limited scope of information. Finally, the trials testing curative treatments in solid tumors showed the highest centrality and the most influential group was the ECOG. We conclude that the chances of discovering life-saving treatments are directly related to the richness of social interactions between researchers inherent in a preferential interaction model.
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Social network integration: A comparison of same-race and interracial roommate relationships
Natalie Shook & Russell Fazio
Group Processes & Intergroup Relations, May 2011, Pages 399-406
Abstract:
The purpose of the study was to identify factors that promote the integration of an outgroup member into an individual's social network, thus enhancing extended contact. White freshmen randomly assigned to either a white or black roommate completed measures of intergroup anxiety and roommate relationship quality at the beginning of their first term at college. At the end of the term, participants reported the extent to which their roommate was integrated into their social network. In general, black roommates were less integrated into the white participants' social networks than white roommates. However, roommate integration also depended on relationship quality and intergroup anxiety. For those with lower quality roommate relationships, integration was generally low. For those with higher quality relationships, lower intergroup anxiety enhanced the likelihood of the integration of a black roommate relative to a white roommate. The results highlight factors that may facilitate or inhibit extended contact.
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Does the promotion of community social capital reduce obesity risk?
Jangho Yoon & Timothy Brown
Journal of Socio-Economics, May 2011, Pages 296-305
Abstract:
We explore whether higher levels of community social capital reduce the likelihood of being obese in the U.S. adult population. We also examine whether this relationship may differ by levels of schooling. Data come from the 2001 to 2005 Behavioral Risk Factor Surveillance System for all 50 U.S. states and the District of Columbia, and are augmented with a validated measure of community social capital, the Petris Social Capital Index. We find that greater community social capital reduces adult obesity risk, and has a larger effect on persons with more schooling. Social capital affects obesity through the promotion of weight-control efforts.
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The Relationship Between Facebook and the Well-Being of Undergraduate College Students
Maria Kalpidou, Dan Costin & Jessica Morris
Cyberpsychology, Behavior, and Social Networking, April 2011, Pages 183-189
Abstract:
We investigated how Facebook use and attitudes relate to self-esteem and college adjustment, and expected to find a positive relationship between Facebook and social adjustment, and a negative relationship between Facebook, self-esteem, and emotional adjustment. We examined these relationships in first-year and upper-class students and expected to find differences between the groups. Seventy undergraduate students completed Facebook measures (time, number of friends, emotional and social connection to Facebook), the Rosenberg Self-Esteem Scale, and the Student Adaptation to College Scale. First-year students had a stronger emotional connection to and spent more time on Facebook while they reported fewer friends than upper-class students did. The groups did not differ in the adjustment scores. The number of Facebook friends potentially hinders academic adjustment, and spending a lot of time on Facebook is related to low self-esteem. The number of Facebook friends was negatively associated with emotional and academic adjustment among first-year students but positively related to social adjustment and attachment to institution among upper-class students. The results suggest that the relationship becomes positive later in college life when students use Facebook effectively to connect socially with their peers. Lastly, the number of Facebook friends and not the time spent on Facebook predicted college adjustment, suggesting the value of studying further the notion of Facebook friends.
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Specialized knowledge and the geographic concentration of occupations
Todd Gabe & Jaison Abel
Journal of Economic Geography, forthcoming
Abstract:
This article examines the effects of specialized knowledge on the geographic concentration of occupations across US metropolitan areas. Controlling for a wide range of other attributes, empirical results reveal that occupations with a unique knowledge base exhibit higher levels of concentration than those with generic knowledge requirements. This result is robust to the use of several model specifications and instrumental variables estimation that relies on an instrument set representing the means by which people acquire knowledge. Thus, the study suggests that the benefits of labor market pooling are particularly apparent in cases where workers require a specialized knowledge base.
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The Externalities of Strong Social Capital: Post-Tsunami Recovery in Southeast India
Daniel Aldrich
Journal of Civil Society, Spring 2011, Pages 81-99
Abstract:
Much research has implied that social capital functions as an unqualified 'public good', enhancing governance, economic performance, and quality-of-life. Scholars of disaster have extended this concept to posit that social capital provides non-excludable benefits to whole communities after major crises. Using qualitative methods to analyse data from villages in Tamil Nadu, India following the 2004 Indian Ocean tsunami, this article demonstrates that high levels of social capital simultaneously provided strong benefits and equally strong negative externalities, especially to those already on the periphery of society. In these villages, high levels of social capital reduced barriers to collective action for members of the uur panchayats (hamlet councils) and parish councils, speeding up their recovery and connecting them to aid organizations, but at the same time reinforced obstacles to recovery for women, Dalits, migrants, and Muslims. These localized findings have important implications for academic studies of social capital and policy formation for future disasters and recovery schemes.
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Social Anxiety as a Basis for Friendship Selection and Socialization in Adolescents' Social Networks
Nejra Van Zalk et al.
Journal of Personality, June 2011, Pages 499-526
Abstract:
Socially anxious children and adolescents have previously been found to have friends with similarly socially anxious, withdrawn behavioral characteristics. How peers might socialize social anxiety over time has, however, not been thoroughly investigated. We examined this in a sample of 834 youths (339 girls and 495 boys; M=14.29), followed for 3 years. We used the social network analysis software SIENA to analyze the data. The results showed that youths who were socially anxious were less popular and chose fewer friends in the network. They also tended to choose friends who were socially anxious, and over time they influenced each other into becoming more socially anxious - over and above other effects. Finally, girls' social anxiety was more influenced than boys' by their friends' social anxiety levels. The results showed the significance of looking at socially anxious youths' friendships over time and embedded in social networks.
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Public avoidance and epidemics: Insights from an economic model
Frederick Chen et al.
Journal of Theoretical Biology, 7 June 2011, Pages 107-119
Abstract:
In this paper, we present a mathematical model of infectious disease transmission in which people can engage in public avoidance behavior to minimize the likelihood of acquiring an infection. The framework employs the economist's theory of utility maximization to model people's decision regarding their level of public avoidance. We derive the reproductive number of a disease which determines whether an endemic equilibrium exists or not. We show that when the contact function exhibits saturation, an endemic equilibrium must be unique. Otherwise, multiple endemic equilibria that differ in disease prevalence can coexist, and which one the population gets to depends on initial conditions. Even when a unique endemic equilibrium exists, people's preferences and the initial conditions may determine whether the disease will eventually die out or become endemic. Public health policies that increase the recovery rate or encourage self-quarantine by infected people can be beneficial to the community by lowering disease prevalence. However, it is also possible for these policies to worsen the situation and cause prevalence to rise since these measures give people less incentive to engage in public avoidance behavior. We also show that implementing policies that result in a higher level of public avoidance behavior in equilibrium does not necessarily lower prevalence and can result in more infections.