1. A computer-implemented method, comprising: accessing time block data for a plurality of time blocks, each time block defining a time period during which programming of a channel is aired; for each time block: identifying devices that were used to present programming of the channel during the time period defined by that time block; and generating first probability data for each identified device, the first probability data including a first probability that the identified device was used to present content on the channel during the time period defined by that time block; for each device, generating second probability data including second probabilities that the device was used to present the content in each time block in sets of two or more time blocks, wherein the second probabilities are based on the first probabilities associated with the time blocks in the sets of two or more time blocks; and generating reach data for a campaign, the reach data based on the first and second probabilities and representative of a reach of the campaign to be presented in the time blocks.