UPDATE: This post is old, and uses a fairly weak method for measuring peak age. I have conducted a thorough analysis published in Journal of Sports Sciences that finds peak age occurs around 29–30.
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Judging the peak age of baseball players is an interesting problem. Over the course of a player’s career, many factors may affect his numbers that have little to do with age: injuries, differing park factors, changes to the run environment of the league, long-run contract incentives, etc. I have looked at the peak ages of pitchers and hitters before (see the right sidebar for links), and I’m happy with the results of found, despite the potential problems. But, I’ve thought about another way to find peak age. Instead of looking at the changing performance of players with long careers, I wanted to look at those with short careers.
Players with short careers typically play only during their peak years. Only when they are at their best are these players providing “major league” level of talent. Both before and after, their skills are not good enough to keep them in the league. Therefore, I’m going to put all of the stats aside and only look at the average age of players with three years or less of major league experience. The average of these short-timers should tell us something about when players peak. I used a recent sample of players from 1980-2002. By excluding 2003-2005 I exclude young players with three year careers who may have much longer careers.
For both hitters and pitchers, the median age of players with careers of three years or less is 26. The mean age for hitters is 26.02 with a standard deviation of 2.37 years. The mean age for pitchers is 26.33 with a standard deviation of 2.82 years. Interesting. I haven’t though much about this other than I thought it would be a neat study to do. Comments, as always, are welcome.