centralization vs narrowing

centralization

noun
  • The act or process of centralizing, or the state of being centralized; the act or process of combining or reducing several parts into a whole 

narrowing

noun
  • The part of a stocking that is narrowed. 

  • The process of becoming narrow. 

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