flea market vs shopping center

flea market

noun
  • A permanent indoor market of stalls in a warehouse selling inexpensive antiques, outdated goods, curios, etc. 

  • An outdoor temporary market selling inexpensive antiques, curios etc. 

shopping center

noun
  • An area, either enclosed or unenclosed, hosting multiple retail establishments; a shopping mall. 

How often have the words flea market and shopping center occurred in a corpus of books? (source: Google Ngram Viewer )