Abstract: Methods and apparatus disclosed herein can be used to perform co-viewer adjustment. An example apparatus or viewership adjustment includes at least one memory, machine readable instructions, and processor circuitry to execute the machine readable instructions to determine compliant and non-compliant household panel meter data based on household metrics for past household viewing behavior, adjust undercounted viewership data based on an active media session interval associated with the household metrics, adjust overcounted viewership data based on a viewership model, the viewership model trained using the compliant household panel meter data, and output adjusted viewership data based on the adjusted undercounted viewership data and adjusted overcounted viewership data.

Abstract: Methods, apparatus, systems, and articles of manufacture are disclosed to determine digital audience reach across multiple platforms. An example apparatus includes audience data receiver circuitry to obtain first audience data from a first media platform; and processor circuitry to perform at least one of the first operations, the second operations, or the third operations to instantiate: activity analyzer circuitry to determine media activities in the first audience data; adjustment analyzer circuitry to: apply at least one adjustment factor to the first audience data based on a source of the audience data; apply a coverage factor adjustment to the first audience data; and output the adjusted first audience data as a deduplicated audience for the first media platform.