constrained vs incentive

constrained

adj
  • Forced; compelled. 

  • Kept within close bounds; confined. 

incentive

adj
  • Inciting; encouraging or moving; rousing to action; stimulating. 

  • Serving to kindle or set on fire. 

noun
  • Something that motivates, rouses, or encourages. 

  • A bonus or reward, often monetary, to work harder. 

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