highway robbery vs unwarranted

highway robbery

noun
  • The act of robbing a traveler on a public road. 

  • Said of excessive or exorbitant prices. 

unwarranted

adj
  • Unjustified, inappropriate or undeserved. 

  • Not warranted; being without warrant, authority, or guaranty; unwarrantable. 

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