In the age of the one-and-done college player, the NBA draft has understandably skewed younger. With our NBA Draft Data Tool, we can get a good look at just how much younger the draft has become and how those younger players have performed compared with their elders.
(A note about the age data in the draft tool. Basketball-reference.com does not have age data for players who never reached the NBA. The data below reflects players' ages on the date of their respective drafts.)
(For an explanation of the methodology and what win shares, expected win shares, and percentage of expected win shares are — and why we're only studying the first 54 picks — read the first entry in this series.)
It shouldn't come as a surprise that younger players, particularly draft-day 19-year-olds, make up more of the draft class than ever before. No 17- or 18-year-olds were picked before 1996, but from that year until 2006, when the NBA's one-and-done rule went into effect, 3.5 players in that age group were selected per year. Generally, they were selected later than younger players in recent years, so when they turned out to be good, the return on expected win shares was very high: That group from '96-'06 has earned 314.3 percent of their expected win shares. Fewer in that age group are selected now, since most players aren't eligible until they're 19.
Also interesting is what has happened to the older players, 22 and over. Yes, fewer of them are being picked, and when they are, it's happening later:
Over the last 10 years, however, the league has done a better job of properly valuing older players. When they were being picked more often and earlier, from '77 to '06, the 22-and-over group returned 87.8 percent of their expected value. Over the last 10 years, when they have been picked less often and later, their return over value has been 103.5 percent.