convenience store vs shopping center

convenience store

noun
  • A small retail store, often in a residential area, that carries a limited selection of items such as staples, junk food, and drugstore items, and which is open long hours for the convenience of shoppers. 

shopping center

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

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