peerage vs ruling class

peerage

noun
  • Peers as a group; the titled nobility or aristocracy. 

  • The rank or title of a peer or peeress. 

  • A book listing such people and their families. 

ruling class

noun
  • The social class of a given society that controls that society's political agenda, whether as formal aristocracy or party leadership or as an informal unit within democracies. 

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