pro rata vs proportionately

pro rata and proportionately both are adverbs.

Word	Noun	Adjective	Verb	Adverb
pro rata	No	No	No	Yes
proportionately	No	No	No	Yes

As adverbs, pro rata and proportionately are synonyms defined as:

pro rata and proportionately: in a way that agrees in amount, magnitude or degree

pro rata (adverb)	proportionately (adverb)
in a way that agrees in amount, magnitude or degree	to a proportionate degree
	in a way that is in correspondence among the constituents of another entity
	in a way that agrees in amount, magnitude or degree