expedience vs self-interest

expedience

noun
  • The quality of being fit or suitable to cause some desired end or the purpose intended; propriety or advisability under the particular circumstances of a case. 

  • Something that is expedient. 

  • Speed, haste or urgency. 

self-interest

noun
  • One's personal interest or advantage, especially when pursued without regard for others. 

How often have the words expedience and self-interest occurred in a corpus of books? (source: Google Ngram Viewer )