The draft: Old vs. Young High School Hitters

I think it's a good idea to shift our attention to topics other than whether the Astros will be moved to the AL.   Rany Jazayerli at Baseball Prospectus recently wrote a series of articles contending that MLB teams' drafting/scouting practices do not adequately account for the difference in age between old and young high school hitters. I don't know if he is right, but if he is on to something, Astros fans should be particularly interested in what he has to say.  After all, the Astros will have to the top pick in 2012; and the 2012 draft, in general, may be one of the most important in team history.  B-Pro published part I and part II of the series.  The article has some critics, and you can see some skepticism in the comments at Baseball Think Factory.

Jazayerli studied two large samples of drafted high school hitters and concluded that only a few months difference in the age of the players when they were drafted resulted in a significant difference in career performance relative to expectations.  (The point of comparison is the career performance expected for players selected at that level in the draft.)  You can read the articles to get a more detailed description of the methodology. The study divided the 17 to 19 year old age range into very young, young, average, old, and very old. (18 years 201 days old is "very old" in the study, which seems humorous to those of us who are actually old.)  Rather than attempt to summarize his conclusions, I will excerpt some quotes.

Let me repeat that: a team that drafted one of the five youngest high school hitters selected among the top 100 picks could expect MORE THAN TWICE AS MUCH VALUE from him as a team that selected one of the five oldest high school hitters. And that’s not a small sample size fluke; that’s a result derived from 32 years of the draft, looking at 160 players from both camps...Young high school hitters are simply much more likely to develop into stars, particularly players who weren’t elite picks...This is, all modesty aside, quite possibly the most impressive and significant finding of my career. When it comes to the drafting of high school hitters, even slight differences in age matter. At least when it comes to high school hitters, young draft picks are a MASSIVE market inefficiency.

Examples of some of the youngest players of the draft in particular years: Ken Griffey Jr., Ricky Henderson, George Brett, Alex Rodriguez, Gary Sheffield, Derek Jeter, Jimmy Rollins, and Jason Kendall.  More quotes from the article:

According to the data, it appears that the importance of a draft pick’s age has, in fact, changed over time… but not in the direction you’d expect: the advantage enjoyed by young players increased dramatically from 1997 to 2003. The average return from the youngest 20 percent of draft picks during this span was more than triple the return of the oldest 20 percent... If a player who might look like a third-round pick on talent alone happens to be a full year younger than his draft class, he ought to be considered a late-first-round pick....The conclusion is clear: at least as recently as 2003, the baseball industry as a whole massively underrated the importance of age in drafting high school hitters and massively undervalued high school hitters who still needed their parents’ permission to sign their contract.

I haven't attempted to evaluate the ages of all of the high school hitters drafted by the Astros in the last few years.  But the Astros have used first round picks in 2009 and 2010 on high school position players.  Jio Miers would fit in the "old player" category set out in the article.  Delino Deshields, Jr. is a "young player," according to the article's criteria.  The implication of the study is that the DDJ has better odds than Miers, in terms of future career performance.

How does this affect possible high school hitters who could be taken with the first pick in 2012?  Nick Williams and Trey Williams are two high school hitters which have been mentioned at TCB.  Nick Williams will be an older high school player on draft day (based on the article's criteria), and Trey Williams will be an average age high school player.  Trey  is about six months younger than Nick.   The implication of the article is that if both players are ranked as approximately equal on draft day, Trey Williams should be favored. 

As I said, I'm still thinking about the conclusions of the article, and I'm not certain how much weight to give them.  That's why I welcome your thoughts.