Guoyu vs Standard Mandarin

Guoyu

name
  • The standardized spoken Chinese language, also referred to as Standard Mandarin. The term remains in common use in the Republic of China (Taiwan) and colloquially in Hong Kong (along with Putonghua). In mainland China, Guoyu or Taiwan Guoyu is used to refer to Taiwanese Mandarin (standard), as opposed to mainland standard Mandarin. 

  • The language the Emperor of China spoke. 

Standard Mandarin

noun
  • The official language of the People's Republic of China and the Republic of China, based on the Beijing dialect of Mandarin and accepted as a lingua franca for Han communities worldwide. 

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