inconsistency vs instability

inconsistency

noun
  • The state of being inconsistent. 

  • An incompatibility between two propositions that cannot both be true. 

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. 

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