Mike McCann at Sports Law Blog has an interesting chart and some reflections on the new NBA minimum draft age, looking specifically at patterns of NBA players getting in trouble with the law (a proxy for personal maturity). Mike has been critical of the NBA's decision to raise the draft age with the intent of excluding kids from going straight to the NBA out of high school and his evidence presented here makes a pretty strong case.
First, college education does not appear to diminish the probability of a player getting in trouble with the law.
Second, players appear more likely to get in trouble with the law towards the middle and end of their careers than at the start.
No matter the interpretation, it doesn't appear that the recent decision by the NBA and NBPA to raise the age of NBA draft eligibility from 18 to 19 (or one year out of high school) will improve the overall law-abidingness of NBA players. If anything, actually, this data suggests that it might have the opposite effect.
My view is that raising the draft age by one year will likely just increase the corruption in high school and college basketball. If I had to predict, I suspect that the response will be to just increase the bidding among the Oak Hill Academy-type programs for players to do one year of prep school or for lower-ranked schools to try to grab guys for one year. Either way, I suspect that the corruption in the system is likely to increase.
Overall, I think that raising the draft age by one year will likely have some serious unintended consequences. They may have either been better off keeping it the same and allowing high schoolers to go straight to the pros or moving to an NFL-type system where kids actually have to commit to college for a few years. The current compromise seems like the worst of all worlds.