cheapen vs deteriorate

cheapen

verb
  • to decrease the value of; to make cheaper 

  • to become cheaper 

  • to make vulgar 

deteriorate

verb
  • To make worse; to make inferior in quality or value; to impair. 

  • To grow worse; to be impaired in quality; to degenerate. 

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