instability vs substantiality

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. 

substantiality

noun
  • The state of being substantial. 

  • The extent to which something is substantial. 

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