instability vs symmetry

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. 

symmetry

noun
  • Exact correspondence on either side of a dividing line, plane, center or axis. 

  • The satisfying arrangement of a balanced distribution of the elements of a whole. 

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