When are upvoted answers listed above accepted answers?

Question

Occasionally on AskUbuntu, I've seen highly upvoted answers listed before the accepted answer for a question. This is useful for when the OP accepts a suboptimal or incorrect answer.

However, when does this phenomenon occur? For some questions it clearly doesn't. Is there a mathematical ratio of upvotes vs. downvotes? If so, what is the ratio?

Answer 1

The highest voted answer is listed first if the accepted answer is made by the OP. See Why are the accepted answers always on the top of the answer list? for details.

Note that you can choose how to sort answers. Currently it is possible to sort by activity, date and votes. The latter is the default.