Gregg Doyle of CBS' Sportsline writes
The gap between the No. 1s and No. 16s continues to shrink, reaching an all-time low this season. In 1998, the No. 1s' average margin of victory was 42.3. In 2001 it was 37. In 2002 it was 29.8. Last year it was 25. This year? Down to 15.5. Three games were decided by 12 points or fewer, another first.
I've seen and read similar things regarding #5 v. #12 and so on. Whether these figures reflect a real narrowing of the differences in teams or not is still open to question. Assuming that the differences are narrowing, the drain of players at younger ages to the NBA has likely played a role.
The earlier movement of players to the NBA reduces the advantage of top teams in two ways. First, it increases the uncertainty in recruiting. If I'm a coach at a top program, do I go after the best high school players, as I would have ten years ago, only to see them opt for the NBA, or play a year or two and skip to the NBA, or do I try to recruit very good players likely to stick around longer? The other influence is based on the distribution of talent. If talent follows a bell-shaped distribution, then the top programs pick off the players at the extreme upper "tail" of talent leaving other programs to pick less talented players. A reduction of the players at the upper end means that top teams must pick from lower skill levels where there skill distribution is not so rare -- the "fatter" part of the bell. In other words, there are a lot more good players in the upper 10 percent of skill level than in the upper 1 percent. When the upper 1 percent (or whatever) is lopped off, the big boys do not have the same advantage.