ghostwriter vs reviewer

ghostwriter

noun
  • A professional writer who is paid to write material that is officially credited to another person; one who writes on behalf of someone else, often for a celebrity. 

  • Smith was listed as the author of his autobiography, but a ghostwriter did most of the work. 

reviewer

noun
  • A person who writes reviews for a newspaper or other publication; a critic. 

  • An inspector. 

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