Is there a bug with the acceptance rate calculation? Just spotted this question, where the user currently has a displayed 57% acceptance rate. I had a look at profile for the user, and found that he'd asked 10 questions, and accepted 4 answers, which by my reckoning is an acceptance rate of 40%. I'm guessing I'm likely missing something? I did wonder if the rate was calculated across all the SE sites, but I see many users (including this one - and myself) with different acceptance rates across different SE sites.

Questions without answers don't count against your acceptance rate.

It would be unfair to penalize someone for not accepting something that doesn't exist.

This my also apply if all the answers are negative, but I'm speculating.