vacancy rate vs percentage

vacancy rate and percentage both are nouns.

Word	Noun	Adjective	Verb	Adverb
vacancy rate	Yes	No	No	No
percentage	Yes	No	No	No

As nouns, percentage is a hypernym of vacancy rate; that is, percentage is a word with a broader meaning than vacancy rate:

vacancy rate: the percentage of all rental units (as in hotels) that are unoccupied or not rented at a given time
percentage: a proportion in relation to a whole (which is usually the amount per hundred); ten percent

Other hypernyms of vacancy rate include pct, per centum, percent.

vacancy rate (noun)	percentage (noun)
the percentage of all rental units (as in hotels) that are unoccupied or not rented at a given time	assets belonging to or due to or contributed by an individual person or group
	a proportion in relation to a whole (which is usually the amount per hundred); ten percent