escalate vs taper off

escalate

verb
  • To climb. 

  • To increase (something) in extent or intensity; to intensify or step up. 

  • In technical support, to transfer a customer, a problem, etc. to the next higher level of authority 

taper off

verb
  • To diminish or lessen gradually; to become smaller, slower, quieter, etc. 

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