occupancy vs period of occupancy

occupancy

noun
  • The act of occupying, the state of being occupied or the state of being an occupant or tenant. 

  • The specific use to which something occupied is put. 

  • The period of time during which someone rents or otherwise occupies certain land or premises. 

period of occupancy

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