discount store vs dollar store

discount store

noun
  • A type of department store which sell products at prices lower than those asked by other department stores. 

dollar store

noun
  • A retail store selling inexpensive items, especially one in which all items have a price of one dollar. 

  • A government-owned shop in Cuba that sold goods mainly to foreigners and solely in exchange for hard currency. 

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