impairment vs unstableness

impairment

noun
  • A deterioration or weakening 

  • The result of being impaired 

  • A downward revaluation, a write-down. 

  • A disability or handicap 

  • an inefficient part or factor. 

unstableness

noun
  • The quality of being unstable; instability 

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