Figure 2

Twitter data and the shadow profiles problem. The left panel shows a schema of the data used in this study. We count with a set of ego users who are connected to their alters through links based on their Twitter replies. The right panel shows the shadow profile problem. For each ego user, we count with preceding alters that had already joined Twitter at the time when the ego joined. Out of those preceding alters, some disclosed their contact lists in Twitter (red) and others did not (blue). The shadow profile problem consists of the inference of personal information of the ego user based only on the information given by disclosing preceding alters, ignoring all data from non-disclosing preceding alters and alters that joined Twitter after the ego user.