disrepair vs retrogression

disrepair

noun
  • The state of being in poor condition, in need of repair. 

verb
  • To get into a state of disrepair. 

retrogression

noun
  • A deterioration or decline to a previous state. 

  • A return to a less complex condition. 

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