impairment vs upper hand

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. 

upper hand

noun
  • Advantage or control. 

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