1. A method, comprising: receiving, at a first server of a database proprietor, a first network communication from a client device, the first network communication including an audience measurement entity cookie identifier of an audience measurement entity cookie, the audience measurement entity cookie set in the client device by a second server of an audience measurement entity; generating, with a processor of the database proprietor, a cookie mapping of the audience measurement entity cookie to a database proprietor cookie, the database proprietor cookie set in the client device by the first server of the database proprietor; and sending a re-direct message to cause the client device to send the cookie mapping to the audience measurement entity associated with the audience measurement entity cookie, the re-direct message including a database proprietor cookie identifier of the database proprietor cookie, the audience measurement entity cookie identifier, and an indication of association between the database proprietor cookie identifier and the audience measurement entity cookie identifier.