For the many viewers whose favorite shows are scattered across different streamers, or those simply searching feverishly for NCIS, Amazon is often the perfect solution. Prime Video, after all, doesn’t just offer its originals alongside acquired shows and movies. It also serves as a platform for almost every other major streamer: HBO Max, Paramount+, Starz, Apple TV, etcetera—all available through the same app. But in solving one problem for consumers, Amazon has created another for analysts and advertisers: No one really knows who’s watching what. How much of the engagement on Prime Video—which all feeds into Nielsen’s increasingly important monthly Gauge ranking—is actually coming from Amazon content? How much from the add-on services? And does it even matter?