I looked up Stockton home/away dispairty. He apparently averaged 11.4 assists per game at home, and 10.6 on the road. A difference of 0.8, which I think is reasonable given that teams score less on the road than they do at home, so it would make sense that their PG would get fewer assists on the road.
I can't find a site that have the splits though, send me a link to one if you don't mind, I'm curious to see what the differences are for other players.
Thats higher than Nash, GP, and Billups combined IIRC. I know Rondo has a similar figure and I always felt the scorekeepers were generous to him.