PRC vs People's Republic of China

PRC

noun
  • A person from the People's Republic of China, especially in contrast to native-born Singaporean Chinese. 

People's Republic of China

name
  • Official name of the country popularly known as China, as opposed to the Republic of China (Taiwan). 

How often have the words PRC and People's Republic of China occurred in a corpus of books? (source: Google Ngram Viewer )