disimprovement vs downtrend

disimprovement

noun
  • Reduction from a better to a worse state. 

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

downtrend

noun
  • Any gradual movement towards a lower state or value. 

verb
  • To undergo a downward trend. 

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