Inferring social ties from geographic coincidences

Investigates the extent to which social ties between people can be inferred from co-occurrence in time and space. If two people live in the same geographic location at the same time, how likely are they to know each other? This question has profound privacy implications, particularly for the ways in which social structures can be inferred from public online records that capture individuals' physical locations over time. Develops a statistical framework to answer such questions using publicly available data from a social media site, and concludes that even a very small number of co-occurrences can result in a high empirical likelihood of a social tie.