In this paper we test the celebrated `Strength of weak ties' theory of Granovetter (1973). We test two hypotheses on the network structure in a data set of collaborating economists. While we find support for the hypothesis of transitivity of strong ties, we reject the hypothesis that weak ties...

We study the social structure of Facebook ‘‘friendship'' networks at one hundred American colleges and universities at a single point in time, and we examine the roles of user attributes -- gender, class year, major, high school, and residence -- at these institutions. We investigate the...