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We examine the likelihood that a pair of sustained telephone contacts (e.g. friends, family, professional contacts, called “friends”) uses the city similarly. Using call data records from Jiamusi, China, we estimate a proxy for the daily activity spaces of each individual subscriber by interpolating the points of geo-located cell towers he or she uses most frequently. We then calculate the overlap of the polygonal activity spaces of two established telephone contacts, what we call linked activity spaces.

Our results show that friends and second-degree friends (e.g. friends of friends) are more likely to geographically overlap than random pairs of users. Additionally, individuals with more friends and with many network triangles (connected groups of three friends) tend to congregate in the city’s downtown at a rate that surpasses randomness. We also find that the downtown is used by many social groups but that …