instability vs prudence

instability

noun
  • The quality of being unstable. 

  • A state that is not in equilibrium, or in which a small change has a large irreversible effect. 

prudence

noun
  • The quality or state of being prudent 

  • economy; frugality. 

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