I don't have the data on voting trends but I can assure you that votes on issues are an important factor that I use when deciding what our FRONTEND and BACKEND teams work on. I don't just look at raw voting numbers either - older issues naturally gather more votes over time even though a newer issue might be more pressing.
(Other factors are: whether it has solution patches; is a security bug; is affecting Moodle Partners; and is part of the major roadmap)
As I'm sure you know, there are always more issues than resources to solve them, and tough choices have to be made all the time.