centralization vs dispersal

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 

dispersal

noun
  • The act or result of dispersing or scattering; dispersion. 

  • A dispersal prison. 

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