assess vs prove out

assess

verb
  • To determine, estimate or judge the value of; to evaluate 

  • To impose or charge, especially as punishment for an infraction. 

  • To calculate and demand (the tax money due) from a person or entity. 

prove out

verb
  • To demonstrate the feasibility of; to show or be shown to be feasible, accurate, true, satisfactory, as expected, hoped, stated, etc. 

  • To turn out to be feasible, accurate, true, satisfactory, as expected, hoped, stated, etc. 

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