I thought about this too. One related point is active users. Some folks were active then left. Sam_Odio's most recent submission is 55 days old. I think karma/

I thought about this too. One related point is active users. Some folks were active then left. Sam_Odio's most recent submission is 55 days old. I think karma/day, over the last N days, would be a fine measure. Also, I think comment-karma/day would be the best measure. It is easier to get points by reposting titles of other people's work as submissions than through thoughtful comments.