centralization vs decentralization

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 

decentralization

noun
  • The action of decentralizing, or the state of being decentralized. 

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