occupancy rate vs per centum

occupancy rate and per centum both are nouns.

Word	Noun	Adjective	Verb	Adverb
occupancy rate	Yes	No	No	No
per centum	Yes	No	No	No

As nouns, per centum is a hypernym of occupancy rate; that is, per centum is a word with a broader meaning than occupancy rate:

occupancy rate: the percentage of all rental units (as in hotels) are occupied or rented at a given time
per centum: a proportion in relation to a whole (which is usually the amount per hundred); ten percent

Other hypernyms of occupancy rate include pct, percent, percentage.

occupancy rate (noun)	per centum (noun)
the percentage of all rental units (as in hotels) are occupied or rented at a given time	a proportion in relation to a whole (which is usually the amount per hundred); ten percent