By Henry Abbott

That's an NBA axiom. But is there evidence it's really true?

Basically, the answer is yes. All defensive measurements are crude. But some smart ones are clear that age helps in the NBA. Point guards are a bit of an exception -- that a position where the speed of youth matters a ton. Players over 34 really don't look to be improving anymore. And a lot of go-getter 22 or 23 year olds (before the injuries set in?) can be effective.

But in general, this evidence suggests you can expect young players to become better defenders with age.

UPDATE: A very interesting development. The first cut of this research found older players played better defense. But was that because the same players were getting better at defense, or because the bad defensive players were losing their jobs, leaving the league and skewing the stats? Based on some reader feedback, however, researcher Jon Nichols did a quick update and found that a lot of what he found in the first cut is really explainable by the fact that good defenders stick around the NBA longer. Very interesting.