instability vs irresolution

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. 

irresolution

noun
  • Lack of resolution; lack of decision or purpose; vacillation. 

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