unequivalence vs unevenness

unequivalence

unevenness

noun
  • A rough or uneven thing. 

  • The quality or characteristic of being uneven; irregularity; inconsistency; the lack of smoothness or continuity. 

  • The result or product of being uneven. 

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