imply vs lead up to

imply

verb
  • to have as a necessary consequence 

  • to suggest by logical inference 

  • to hint; to insinuate; to suggest tacitly and avoid a direct statement 

lead up to

verb
  • To set in motion; to act as a causal or preparatory event or sequence of events. 

  • To follow or mark a path toward. 

  • To precede in time. 

How often have the words imply and lead up to occurred in a corpus of books? (source: Google Ngram Viewer )