What I understood of the utility of the audience measurement

For radio stations, but also for other media, audience measurement allows teams selling advertising space to give it a value and promote to buyers. It also allows teams that are responsible for programs to identify who listens to what, on what stations and thus to adjust programs. For advertisers and agencies, audience measurement allows, before a campaign, to identify areas with the best cost / audience to maximize the effectiveness of their advertising targets of their campaigns. During and after the campaign, it permits evaluation its impact on advertising pressure and (sometimes) on the cover.