free rider vs freeloader

free rider

noun
  • One who obtains benefit from a public good without paying for it directly. 

  • A worker at an open shop who is able to enjoy the benefits negotiated by a union without being a member of the union. 

  • Someone who obtains goods or services legally without paying. 

freeloader

noun
  • One who does not contribute or pay appropriately; one who gets a free ride, etc. without paying a fair share. 

  • An individual who takes expired unsold merchandise from the back of supermarket premises. 

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