We have an annual cleanup which basically only turns the title to a question in a grammatical sense, independent from their status (accepted answer).
I looked a bit through the unanswered questions and I came to the impression that they can be divided into three different cases:
Question has a really good answer, sometimes even with positive feedback in comments by the author, but no acceptance.
Question has no answer at all, although answerable.
Question seems to be hardly answerable, which manifests in either no or a great number of totally different answers.
I'm not sure wether we could do anything about 1), despite pinging the OP and asking wether one of the answers is acceptable. Are there moderation tools to force acceptance? Seems counter-intuitional.
But 2) could be improved by pushing up them so that they get some attention and eventually answers are generated and accepted (like I tried here).
And finally, 3) should in all consequence lead to [on hold] or [closed] status.
Any thoughts about this? The main idea would, of course, be improvement of the % answered score.
Edit as per the comment of @fileunderwater
I will try to push/answer questions without positively voted answers...