METHODS AND APPARATUS TO DETERMINE HEADPHONE ADJUSTMENT FOR PORTABLE PEOPLE METER LISTENING TO ENCODED AUDIO STREAMS

Methods, apparatus, systems and articles of manufacture to determine headphone adjustment for portable people meter listening to encoded audio streams are disclosed. Example apparatus disclosed herein include a meter data analyzer to determine audience estimates for streaming media; a headphone survey analyzer to calculate a global lift factor based on a determined proportion of the audience that listens to streaming media via headphones and a determined proportion of the audience that listens to streaming media without headphones; a headphone survey adjuster to: calculate adjustment factors for a plurality of unique demographic adjustment groups; an audience adjustment calculator to apply the adjustment factors to the audience estimates for streaming media, wherein the adjustment factors are applied to audience members in the audience estimates that are associated with respective unique demographic adjustment groups; and report new audience estimates based on the audience estimates with the applied adjustment factors.