Disclosed example audience measurement apparatus determine a first audience metric based on set-top box return path tuning data obtained from set-top boxes located in a first geographic area; determine a second audience metric from a portion of audience measurement data corresponding to a second geographic area, the portion of the audience measurement data associated with monitored sites in the second geographic area having second set-top box characteristics that correspond with first set-top box characteristics of the set-top boxes located in the first geographic area; determine ratios of (i) respective first audience metrics determined for respective demographic stratifications to (ii) corresponding second audience metrics determined for the respective demographic stratifications; and combine the ratios after multiplication with third audience metrics determined, for the respective demographic stratifications, from the audience measurement data to determine an audience exposure metric that estimates exposure to media in the first geographic area.