Comment on Duplicate Content Penalty SEO by SafeNetting.

Duplicate Content Penalty How do you know if you’ve been penalized due to content duplication … I run several 100% content sites that do NOT recycle content — but deal with the exact same subject over and over again. My Google payout has nose-dived and I’m thinking that it’s because we cover a topic so completely.

How do you know?
Does Google tell you?
Is there some place I can find out?