centralization vs clustering

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 

clustering

noun
  • A prewriting technique consisting of writing ideas down on a sheet of paper around a central idea within a circle, with the related ideas radially joined to the circle using rays. 

  • The undesirable contiguous grouping of elements in a hash table. 

  • A grouping of a number of similar things. 

  • The grouping of a population based on ethnicity, economics or religion. 

adj
  • Forming a cluster. 

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