contributor vs fourth estate

contributor

noun
  • A person who produces articles published in a newspaper, magazine, online publication, etc. 

  • A benefactor; someone who donates to charity or some cause. 

  • A person (or thing) instrumental in the creation or growth of something. 

  • A person who backs, supports or champions a cause, activity or institution. 

fourth estate

noun
  • Journalism or journalists considered as a group; the press. 

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