1. A method, comprising: accessing a first set of cookies and a set of user identifiers, the cookies and user identifiers corresponding to devices accessing media via the Internet; identifying, using a processor, a pattern in the first set of cookies; obtaining impression information from a database proprietor, the impression information comprising a second set of cookies; identifying, using the processor, a subset of the second set of cookies that are associated with a same person based on the pattern; and associating, using the processor, impressions corresponding to the identified subset with the same person.