With the fragmentation of TV audiences and the rise of streaming video services like Netflix and Amazon Prime Video that are notoriously guarded with their data, it is becoming progressively more difficult for TV companies and advertisers to know just how popular individual TV shows actually are. Many are increasingly turning to social media as a guide to popularity, but these are demographically skewed.
Source: The Top TV Shows Of 2017, And The Inexorable Rise Of Netflix | Music Industry Blog