We use variation in wind speeds at surfing locations in Switzerland as
exogenous shifters of users' propensity to post content about their
surfing activity onto an online social network. We exploit this
variation to test whether users' social ties on the network have a
causal effect on their content generation, and whether conent generation
in turn has a similar causal effect on the users' abilty to form social
ties. Economically significant causal effects of this kind can produce
positive feedback that generate multiplier e¤ects to
interventions that subsidize tie formation. We argue these interventions
can therefore be the basis of a strategy by the rm to indirectly
faciliate content generation on the site. The exogenous variation
provided by wind speeds enable us to measure this feedback empirically
and to assess the return on investment from such policies. We use a
detailed dataset from an online social network that comprises the
complete details of social tie formation and content generation on the
site. The richness of he data enable us to control for several spurious
confounds that have typically plagued empirical analysis of social
interactions. Our results show evidence for significant positive
feedback in user generated content. We discuss the implications of the
estimates for the management of the content and the growth of the network