Google 翻訳使っていいよ。
Typical
”Among typical couples who initiate use of a method (not necessarily for the first time),
the percentage who experience an accidental pregnancy during the first year if they do not stop use for any other reason.”

Perfect
”Among couples who initiate use of a method (not necessarily for the first time) and who use it perfectly (both consistently and correctly),
the percentage who experience an accidental pregnancy during the first year if they do not stop use for any other reason.”