How about you guys learn to read? I said "young to the NBA", not "young", and no-one specified the time he left Dallas, which was before the 2004-05 season, not the 2003-04 season, which you should know being a Dallas fan. Cherrypicking makes you look like the arsehole, not me.
When Nash arrived in Dallas in 98-99 he was 25 and had played 2 years as a backup in Phoenix - he was "young to the NBA" in that he'd only played 2 years. Remember that PGs and centres often take 5+ years to mature fully in the NBA, and most NBA players peak in their late-20s.
Nash really matured into some semblance of his true NBA form in 2000-01 when he took over the reigns in Dallas and went for 15/7 with near 50-40-90 %s. The next year he went for 18/8. Back then he was playing with Mike Finley, a young Dirk, and not much else in terms of talent, which pretty well explains the lower assist numbers. By contrast, at Phoenix he has always played on talented teams with guys who can finish off his passes.
Further confirmation of the benefit of having great teams around him to help shoulder the load since he's been in Phoenix is that he's had 5 straight 50-40 seasons, and would have 5 straight 50-40-90 seasons but for shooting 0.887 in 04-05, and 0.899 (!) in 06-07.
As I already said in my post above, Nash is a true late-bloomer, but he's been pretty damned good since 2000-01, although the poor teams he played with in the early days in Dallas artificially constricted his numbers across the board. How else do you explain the difference given that he played an up-tempo style in both destinations?
Oh, and if you ers want to take potshots, fine, but if you know this board at all you should also know that I rarely air opinions I haven't thought through and researched. Disagree with me all you like, but stick the "re ed" calls on someone else.