big deal vs who cares

big deal

intj
  • Indicates that something is not important or impressive; so what. 

noun
  • Something very important or difficult; a matter of great concern; a considerable feat or achievement. 

  • Someone very important; a VIP. 

who cares

phrase
  • A reply that diminishes the importance of another speaker's immediately preceding statement. 

  • A reply to an unimportant or irrelevant statement, indicating indifference on the part of the speaker. 

How often have the words big deal and who cares occurred in a corpus of books? (source: Google Ngram Viewer )