This document discusses television ratings and viewership. It provides background on how Nielsen ratings work using a representative sample to track viewership of shows. Some of the top rated shows of 2018 according to Nielsen are listed, including "Roseanne", "The Big Bang Theory", and "This Is Us". The document also discusses how viewership is changing with new platforms and argues ratings may not fully capture viewers who watch on devices outside the home. Alternative methods for measuring popularity using social media and streaming data are presented.