mass media vs public relations

mass media

noun
  • Collectively, the communications media, especially television, radio, and newspapers, that reach the mass of the people. 

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 mass media and public relations occurred in a corpus of books? (source: Google Ngram Viewer )