disimprovement vs retrogression

disimprovement

noun
  • Reduction from a better to a worse state. 

  • attempt to make something better while ending up worse than before. 

retrogression

noun
  • A deterioration or decline to a previous state. 

  • A return to a less complex condition. 

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