title: A natural experiment of social network formation and dynamics.
abstract: Social networks affect many aspects of life, including the spread of diseases, the diffusion of information, the workers' productivity, and consumers' behavior. Little is known, however, about how these networks form and change. Estimating causal effects and mechanisms that drive social network formation and dynamics is challenging because of the complexity of engineering social relations in a controlled environment, endogeneity between network structure and individual characteristics, and the lack of time-resolved data about individuals' behavior. We leverage data from a sample of 1.5 million college students on Facebook, who wrote more than 630 million messages and 590 million posts over 4 years, to design a long-term natural experiment of friendship formation and social dynamics in the aftermath of a natural disaster. The analysis shows that affected individuals are more likely to strengthen interactions, while maintaining the same number of friends as unaffected individuals. Our findings suggest that the formation of social relationships may serve as a coping mechanism to deal with high-stress situations and build resilience in communities.
authors.affiliation: Department of Information Systems, National University of Singapore, 117418, Singapore; and phantq@comp.nus.edu.sg airoldi@fas.harvard.edu.
authors.forename: Tuan Q
authors.initials: TQ
authors.lastname: Phan
authors.affiliation: Department of Statistics, Harvard University, Cambridge, MA 02138 phantq@comp.nus.edu.sg airoldi@fas.harvard.edu.
authors.forename: Edoardo M
authors.initials: EM
authors.lastname: Airoldi
mesh_terms: D055867:Cyclonic Storms; D004190:Disasters; D006801:Humans; D020407:Internet; D007398:Interpersonal Relations; D061108:Social Media; D060756:Social Networking; D013334:Students; D014481:United States; D014495:Universities
keywords: causal inference; natural disasters; natural experiment; propensity score matching; social networks