ahead of the curve vs rearguard

ahead of the curve

prep
  • Above average; generally performing well. 

  • Changing before competitors. 

rearguard

noun
  • The rearmost part of a force, especially a detachment of troops that protect the rear of a retreating force. 

  • The defence, collectively the defenders. 

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