investigative journalism vs mass media

investigative journalism

noun
  • A form of journalism in which the reporter deeply investigates a single topic of interest, often involving crime or corruption. 

mass media

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

How often have the words investigative journalism and mass media occurred in a corpus of books? (source: Google Ngram Viewer )