expect vs require

expect

verb
  • To consider obligatory or required. 

  • To predict or believe that something will happen 

  • To consider reasonably due. 

  • To be pregnant, to consider a baby due. 

require

verb
  • Naturally to demand (something) as indispensable; to need, to call for as necessary. 

  • To demand, to insist upon (having); to call for authoritatively. 

  • To demand of (someone) to do something. 

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