indifferent vs middle-of-road

indifferent

noun
  • A person who is indifferent or apathetic. 

adj
  • Indicating or reflecting a lack of concern or care. 

  • Ambivalent; unconcerned; uninterested, apathetic. 

  • Having no preference. 

  • Mediocre (usually used negatively in modern usage). 

  • Not making a difference; without significance or importance. 

  • Being in the state of neutral equilibrium. 

middle-of-road

How often have the words indifferent and middle-of-road occurred in a corpus of books? (source: Google Ngram Viewer )