Social media treats all users the same: trusted friend or total stranger, with little or nothing in between. In reality, relationships fall everywhere along this spectrum, a topic social science has investigated for decades under the theme of tie strength. Our work bridges this gap between theory and practice. In this paper, we present a predictive model that maps social media data to tie strength. The model builds on a dataset of over 2,000 social media ties and performs quite well, distinguishing between strong and weak ties with over 85 % accuracy. We complement these quantitative findings with interviews that unpack the relationships we could not predict. The paper concludes by illustrating how modeling tie strength can improve social media design elements, including privacy controls, message routing, friend introductions and information prioritization. Author Keywords Social media, social networks, relationship modeling, ties,

Le CIRANO est un organisme sans but lucratif constitué en vertu de la Loi des compagnies du Québec. Le financement de son infrastructure et de ses activités de recherche provient des cotisations de ses organisationsmembres, d’une subvention d’infrastructure du ministère de la Recherche, de la Science et de la Technologie, de même que des subventions et mandats obtenus par ses équipes de recherche. CIRANO is a private non-profit organization incorporated under the Québec Companies Act. Its infrastructure and research activities are funded through fees paid by member organizations, an infrastructure grant from the Ministère de la Recherche, de la Science et de la Technologie, and grants and research mandates obtained by its research teams.

bridging social capital, happiness, satisfaction with life, loneliness, depression, positive affect, negative affect,

Abstract — In this work we use anonymous telecommunication data to investigate how migration influences the dynamics of mobile social networks. We analyze the evolution of social ties for an entire country over a period of 11 months, examining: tie strength, sociality level, distance of ties, and persistence of ties. We find changes in tie strengths pre and post migration, specifically at six months before and a month after migration and discover that on average it takes approximately seven to eight months to restructure ones social network at a new residential location following migration. Moreover, the strongest ties such as those between families and close friends appear to be independent of migration. These ties continue to persist at nearly constant rates, in stark contrast to the weaker ties whose persistence rates drop significantly. Finally, we quantify the interdependency between the persistence rate, social strength, and migration distance; as a result, we are able to estimate how likely a given tie would persist, given the pre-migration social strength and distance of migration. I.