leading vs number-one

leading

noun
  • Vertical space added between lines; line spacing. 

  • An act by which one is led or guided. 

adj
  • Providing guidance or direction. 

  • Occurring in advance; preceding. 

  • Ranking first. 

number-one

How often have the words leading and number-one occurred in a corpus of books? (source: Google Ngram Viewer )