Breaking Down the Aging Curve: Mid 20s

In case you missed parts 1 and 2, you can follow the links especially back to one if you want to see what I am doing.  Otherwise it is time to look at the 24 year old cohort:

There were 362 players in this group, 64 of which only had one season of 300+ PAs, leaving us with 298 in the sample.  Those 298 averaged 7.2 years of full seasons.  Almost 21% of them (62 total) had their best season in year one according to wRC+, and for war it was just below 20% (59).  For those players the average career length was 4.3 and 4 years respectively.  I’m going to start speeding up the discussion only highlighting things of interest so that we can get to a more comprehensive picture.
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The 24 cohort chart shows a couple of years of modest improvement before starting their decline though wRC+ stays pretty flat until age 30 or so.  We have seen some similar patters up to this point, but those are going to end with the next group.

Age 25 Cohort:

This group was comprised of 343 players in total.  After taking out the 59 that only had one season I had 284 left at an average number of 5.9 full seasons.  About 30% of those players had their best season in their first full big league chance (86 for wRC+ and 87 for WAR) with average length of career for the 1st year max group of 4 years for wRC+ and 3.7 for WAR.

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This is where this cohort is getting more interesting.  They seem to only decline as a group after their first full season.  There doesn’t seem to be any appreciable increase in hitting or overall performance throughout their careers.  You will also see that they are therefore nearer their max as a group out of the gate as well.  Once I am through all of the cohorts we can discuss overall threshold of performance relative to these which will help us understand everything that is going on hopefully.

Age 26 Cohort:

Here is where the sample sizes start to shrink again as we get to ages where a lot of players have either quit or will never make it.  There are still 238 players in this group so it is relatively large (4th largest cohort), and 64 had only one full season leaving a group of 174 players who on average had 5.2 full seasons.  65 (37%) maxed out their wRC+ in year 1 along with 54 (31%) maxing WAR right off the bat.  Those groups averaged 3.6 full seasons and 3.3 respectively.

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Like the last group, this group seems to max out on average in their first year and are declining by their late 20s.  They keep up 80 or near 80% of their max in hitting into their mid 30s, but that I think is going to prove out as being two things.  The first will be survivorship issues since on average most of this group retired or were forced out of the game around age 31, and the second being that their starting threshold won’t be as high and will be easier to stay near.

We are getting close.  I will try and blow through the late 20s before the end of the week so I can summarize and give some things that I think are of interest overall.



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