listenership vs viewership

listenership

noun
  • The audience that listens to a certain form or genre of audio material (specifically (Internet, radio), an audio broadcast such as a radio program or a podcast). 

  • The act of paying attention to a conversation or speech; listening. 

viewership

noun
  • collectively, the viewers of a television program or other video broadcast 

How often have the words listenership and viewership occurred in a corpus of books? (source: Google Ngram Viewer )