An example method includes receiving a media identifier and an impression identifier from a device, the media identifier being indicative of media presented at the device; receiving the impression identifier in association with first user information from a first database proprietor as a result of the first database proprietor obtaining a first identifier sent from the device, the first identifier identifying at least one of the device or a user; receiving the impression identifier in association with second user information from a second database proprietor as a result of the second database proprietor obtaining a second identifier sent from the device, the second identifier identifying at least one of the device or the user; identifying the first and second user information as associated with a same user based on the impression identifier; and associating the first and second user information with the media identifier.