I was just curious about this as I currently have a question that only has one answer, and it already has a -1. Now, this question is new, so I am hopeful that somebody will respond appropriately. However, it got me thinking about this.
Per this blog post, any question with 1 answer counts towards your accept rate. But, what if that 1 answer is wrong, and has been acknowledged by the community as wrong?*
*Obviously, there would have to be a threshold. IE. you can't use 1 or else the poster could downvote every answer just to keep their accept rate higher.