bellwether vs signpost

bellwether

noun
  • A stock or bond that is widely believed to be an indicator of the overall market's condition. 

  • Anything that indicates future trends. 

  • The leading sheep of a flock, having a bell hung round its neck. 

signpost

noun
  • A word or phrase within a clue that serves as an indicator, rather than being fodder. 

  • A post bearing a sign that gives information on directions. 

verb
  • To indicate logical progress of a discourse using words or phrases such as now, right, to recap, to sum up, as I was saying, etc. 

  • To install signposts on. 

  • To signal, as if with a signpost 

  • To direct (somebody) to services, resources, etc. 

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