compulsory purchase vs robbery

compulsory purchase

noun
  • The power of a state to expropriate private land within its jurisdiction for public use. 

robbery

noun
  • The offense of taking or attempting to take the property of another by force or threat of force. 

  • The act or practice of robbing. 

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