fourth estate vs public relations

fourth estate

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

public relations

noun
  • The professional dissemination and management of information by a person or an organization to the public with the purpose of creating a favorable public image. 

  • The favorability of the public image of a person or organization. 

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