inequality vs unequivalence

inequality

noun
  • A statement that of two quantities one is specifically less than (or greater than) another. Symbol: < or ≤ or > or ≥ or ne , as appropriate. 

  • The inequality in living standards led to a civil war as the have nots rebelled. 

  • An unfair, not equal, state. 

unequivalence

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