coercive vs obligatory

coercive

adj
  • Displaying a tendency or intent to coerce. 

  • Such that the ratio of |F(x)| to x approaches infinity as x approaches infinity. 

obligatory

adj
  • Imposing obligation, legally, morally, or otherwise; binding; mandatory. 

  • Requiring a matter or obligation. 

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