look down on vs undervalue

look down on

verb
  • To regard or treat as inferior. 

  • To view [people or events on Earth] from the vantage point of the afterlife (originally, Heaven) 

undervalue

verb
  • To have too little regard for. 

  • To underestimate, or assign too low a value to. 

noun
  • An undervaluation; a price or rate below the actual worth. 

How often have the words look down on and undervalue occurred in a corpus of books? (source: Google Ngram Viewer )