Methods and apparatus to generate audience measurement data from population sample data having incomplete demographic classifications

A method comprising:

• accessing, by executing instructions with at least one processor, first network communications received via a first server associated with an audience measurement entity, the first network communications including first beacon request messages, the first beacon request messages indicating first impressions corresponding to media accessed on devices, the first beacon request messages identifying time segments of the media presented at the devices, the time segments corresponding to site census durations;
• causing, by executing instructions with the at least one processor, the first server to send second network communications to the devices, the second network communications including first re-direct response messages redirecting the devices to a database proprietor;
• and
• in response to not receiving demographic information corresponding to the time segments of the media, for ones of demographic groups, calculating demographic durations for ones of the demographic groups based on duration distribution ratios and the site census durations.

A non-transitory computer-readable storage medium having stored thereon computer-readable instructions that, when executed by at least one processor, cause performance of operations comprising:

• accessing first network communications received via a first server associated with an audience measurement entity, the first network communications including first beacon request messages, the first beacon request messages indicating first impressions corresponding to media accessed on devices, the first beacon request messages identifying time segments of the media presented at the devices, the time segments corresponding to site census durations;
• causing the first server to send second network communications to the devices, the second network communications including first re-direct response messages redirecting the devices to a database proprietor;
• and
• in response to not receiving demographic information corresponding to the time segments of the media, for ones of demographic groups, calculating demographic durations for ones of the demographic groups based on duration distribution ratios and the site census durations.