According to the accepted answer by Rick Sladkey to the question Why does the "top X%" in my profile change frequently between week/month/all time? your best overall percentage ranking in the league is displayed on your profile.
The metric reported on your profile under the big score is your best overall percentage ranking in the leagues over the most recent time periods that are collected and reported. To see how you fare in the other categories just check the:
However I noticed that for at least one user, Ernest Friedman-Hill, this doesn't work if the best overall percentage is year.
His profile lists him as "top 2% overall", but if you check on the user leagues he's ranked 145 for the year. The tool tip for the cumulative users with a rep change of +250 for the year is 31,602. Percentage for the year for Ernest is (145/31,602) * 100 = 0.46%, which is better than 2%.
I've also noticed I've never seen Top n% this year for anyone else.
So is my understanding of how to calculate top n% wrong or is Rick Sladkey's answer mostly correct?
My apologies to Ernest for picking on you.