Bachelor of Science vs bachelor's degree

Bachelor of Science

noun
  • A three- to four-year (about 120 credit hours) undergraduate degree, with a concentration in the sciences or scientific applications. 

bachelor's degree

noun
  • The first or lowest academic degree conferred by universities and colleges; a baccalaureate. 

How often have the words Bachelor of Science and bachelor's degree occurred in a corpus of books? (source: Google Ngram Viewer )