clarity vs perspicuity

clarity

noun
  • The state or measure of being clear, either in appearance, thought or style; lucidity. 

  • The ability to be easily understood. 

perspicuity

noun
  • Clarity, lucidity, especially in expression; the state or characteristic of being perspicuous. 

  • Transparency; translucence. 

  • Perspicacity; insight. 

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