dispersal vs propagation

dispersal

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

  • A dispersal prison. 

propagation

noun
  • the dissemination of something to a larger area or greater number 

  • the act of propagating, especially the movement of a wave 

  • winning new converts 

  • some degree of success in the spread of propaganda 

  • the elongation part of transcription 

  • the multiplication or natural increase in a population 

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