lack vs proliferate

lack

verb
  • To be short (of or for something). 

  • To be without, not to have, to need, to require. 

noun
  • A deficiency or need (of something desirable or necessary); an absence, want. 

proliferate

verb
  • To increase in number or spread rapidly; to multiply. 

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