betterment vs furtherance

betterment

noun
  • An improvement. 

  • An improvement to a property that adds to its value. 

furtherance

noun
  • Advancement or progress. 

  • Promotion. 

  • The act of furthering or helping forward 

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