I would say that 27 is the beginning of many position player's prime years, but it's certainly not the peak. I don't know if anyone's ever done a study, but I highly doubt that 27 on average is the most productive year for most players out there. That's actually exactly what somebody did. 27 is the average prime year. That doesn't mean guys fall off cliffs at 28 or 29. What usually happens is players reach their peak at 27, but they can stay relatively close to that peak for several years after, a sort of plateau after the highest height. I find that hard to believe. Gotta link? Unfortunately, since I last read about all this at least 5 or 6 years ago, I don't have a link, but I can back up goony on this. In fact, I thought it to be common knowledge. Sorry, I still don't buy it. Look at the last 10 (different) MVP winners. Look at the All-Star game roster from this last year, and for anyone over 32, what were their most productive years? You had Bonds, not even close. Kent's most productive years were 29-32. Chipper Jones...27, you got that one. Sammy...2001 when he was 32. Larry Walker...30-32. Caminiti...33. Bagwell's best years were 29-33, other than the fluke season when he was 26. Go down the all-star rosters, league leaders in OPS, past MVPs, you'll find the majority of them do NOT have their best years at or before 27. The only explanation I can think of for your claim is your average role player who never does anything significant might peak at 27, and that's why they never did anything significant. I don't know. But looking at the quality players in the league, they don't peak at 27. I don't think Pierre, by any means, has necessarily had his best year. This BP article touchs on it a little bit... http://www.baseballprospectus.com/article.php?articleid=2659 Another Quote... http://www.baseballprospectus.com/library/Offense/Predicting/index.php