sexual assault vs statutory rape

sexual assault

noun
  • A physical attack of a sexual nature on another person or a sexual act committed without explicit consent. 

statutory rape

noun
  • An illegal act of sexual intercourse by an adult with a person under the legal age of consent for sex, or with another adult who is not able to consent because of intellectual disability. 

How often have the words sexual assault and statutory rape occurred in a corpus of books? (source: Google Ngram Viewer )