sparingly vs sparsely

sparingly

adv
  • In a sparing manner; with frugality, moderation, scantiness, reserve, forbearance, or the like; sparsely. 

sparsely

adv
  • In a scattered or sparse manner; widely apart; thinly. 

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