[This is similar in nature to Adrian's question/bulletin How can we encourage more voting? Only more focused on voting on answers.]
I've been on a personal quest to get this site's percentage of questions answered into the 90th percentile. When I started 3 days ago, we were at 86.3% or so and as the time of writing this we are at 87.4%.
If you don't know, the percentage (P) is calculated using the number of questions (Q) displayed here and the number of answers without an upvote (A) displayed here (note: this is not even about the Asker marking an answer as correct).
(Q - A) / Q = P
So, to increase the percentage, we just need to answer questions and upvote GOOD answers. That requires, at minimum, two users involved since you can't upvote your own answers.
From Area 51