Given that karma is cumulative, median is a better measurement. I couldn't spot a standard deviation if it bit me these days, but I would guess the difference between 4 and 3 is significant.
Having said that, a community attracts people like the people it already contains. The more it grows, the greater variety of interests it contains, and therefore the greater number of people with certain, but now differing, interests it attracts.
If you think of it like ripples on a pond, if I'm way out on one edge, I'd likely be vastly different to a user on another edge, though we'd both find some common ground toward the centre. The closer you are to the centre the more you have in common to a greater number of people.
PG is the centre of the pond, so you would expect more people to be more 'like' him, which would lead to more votes. Not bias. Just community.
Having said that, a community attracts people like the people it already contains. The more it grows, the greater variety of interests it contains, and therefore the greater number of people with certain, but now differing, interests it attracts.
If you think of it like ripples on a pond, if I'm way out on one edge, I'd likely be vastly different to a user on another edge, though we'd both find some common ground toward the centre. The closer you are to the centre the more you have in common to a greater number of people.
PG is the centre of the pond, so you would expect more people to be more 'like' him, which would lead to more votes. Not bias. Just community.