Actually, it seems chronological. For each vote value, the most recent is on top. I looked at this for my "9" and "10" votes going back a year, and there is perfect correlation.
I always thought that particular "feature" was somewhat mis-named, since really it is just a ranking of your votes from highest to lowest; nothing too statistical about it.
The "statisically favorite photographer" report is different, since that is based on votes given to the photographer, and not just a single image.
