compulsory acquisition vs compulsory purchase

compulsory acquisition

noun

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

compulsory purchase

noun

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

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