instability vs unrest

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. 

unrest

noun
  • A state of trouble, confusion and turbulence, especially in a political context; a time of riots, demonstrations and protests. 

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