A New Look at Pitcher Aging Patterns

In recent years it seems there's been a huge number of age defying pitchers. According to the research of Bill James, players are supposed to peak at age 27, and have their prime around 27-30, but somebody forgot to tell a lot of current hurlers. Roger Clemens is winning Cy Youngs in his 40s. David Wells was a better pitcher in his late 30s and early 40s than he was a decade earlier. Randy Johnson had a historic peak in his late 30s. Jaime Moyer never topped 14 win shares in a year before turning 35. Since then he's done it five times. Curt Schilling's been far better since turning 30. And then there's Woody Williams, and Kenny Rogers and Kevin Brown, and...

Well, you get the idea. Just how good are current pitchers aging, and more importantly - how well are they aging compared to previous generations?

To figure this I took the info from Bill James's Win Shares book (and its annual updates) and put together a database organized by age of the pitchers for each year of their career. I used every pitcher in major league history who had at least 100 starts and a known birth year - 1179 guys in all. Let's cut the intro and get to the results. First, here's the total list of win shares the pitchers earned at each age:

ALL 1179 PITCHERS - 132,680 WS

Age	WS	% of peak
15   	0	0%
16	8 	0.1%
17	36	0.3
18	162	1
19	685	6
20	1729	14
21	3327	28
22	5198	43
23	7511	63
24	9407	79
25	11153	93
26	11964	100
27	11883	99
28	11286	94
29	10692	89
30	9464	81
31	8430	70
32	6865	57
33	5767	48
34	4661	39
35	3661	31
36	2749	23
37 	1894	16
38 	1450	12
39 	936	8
40  	691	6
41 	481	4
42 	254	2
43	131	1
44 	97	1
45 	53	0.4
46 	23	0.2
47 	21	0.2
48	11	0.1
49	0	0

Looking at this chart, a few things stand out at first glance.

Age 26, not age 27 is the big year for the most pitcher, but it's very close either way. The real lesson I take from this is that there isn't so much a Single Shining Peak Year, as much is there is a standard prime - ages 25-29 here.

There are some problems with this list. First, it includes guys that are too damn young to really tell us anything about aging patterns. Kyle Lohse, Jon Garland, C. C. Sabathia all make the 100 GS cut, but they don't really help us determine when pitchers are peaking. Also, it includes guys from all sorts of different eras - the pitchers box era (1876-1892), the deadball era (defined here as 1893-1919), and the liveball era. The differences in the eras could seriously impact how pitchers aged.

Let's break it down into four groups:

Pitchers' Box Guys

Deadballers

Liveballers born before 1960 (actually, 7/1/59)

Liveballers born in the 1960s

I want to separate the last group because enough of them are still playing and they could gum up the data. Besides, the goal is to see how contemporary pitchers are doing against previous generations. I'm including all pitchers and not just those still playing because to leave out those who were forced out of the game because they weren't that good would skew the data toward old-agers. Jack Armstrong was born within 12 months of Kenny Rogers - just as fair we treat them as such. As for the guys since ‘69, we'll just ignore them for now as they're likely to be a source of noise.

Also, to make the comparisons easier, I'll not look at total Win Shares but at what percentage of the group's peak was reached at each age.

Age	BOX    DEAD   LIVE    1960s
18	6	1	1	0
19	22	6	3	2
20	46	16	8	7
21	69	26	21	14
22	83	47	32	33
23	100	62	50	57
24	90	81	69	73
25	82	94	86	100
26	76	98	100	97
27 	86	100	98	90
28 	57	96	97	96
29	55	84	96	97
30	37	69	90	88
31	28	55	83	82
32	21	43	70	72
33	14	33	62	59
34	10	23	52	50
35	8	16	40	46
36	2	11	32	42*  (1960-8)
37	0.5	8	22	26*  (1960-7)
38	2	5	17	22*  (1960-6)
39	X	3	12	12*  (1960-5)
40	X	4	8	12*  (1960-4)

Baseball was a very different game back in the days of Old Hoss and the gang. They were as good at age 32 as contemporaries are at age 38. Shocking as it sounds, tossing 600 innings a year isn't that good for the arm.

They aged so poorly that it can easily distract one from recognizing how badly deadballers aged. These guys tended to be worked harder in their early 20s than liveballers, and did fine in their prime, but once they hit age 29 they began a very rapid descent. They aged a few years better than box'ers, but a few years worse than liveballers.

So much for the preliminaries, now for the main event: how are contemporaries doing? In a shocking development, I don't see any evidence of improved aging patterns until they reach their mid-30s. The gains are there, but it isn't always easy to see how real it is because at the same time they rise up, they lose some of their pitchers.

This is an important point because there is good reason to think the guys born at in 1968-9 (well, actually from 7/1/67 - 6/30/68 because that's how I set up the database) won't age as well as the earlier bunch. Here's a complete list of guys born in those last 24 months that pitched in baseballin 2004 (ordered from most to fewest win shares):

Flash Gordon, Mike Mussina, Kent Mercker, Cal Eldred, Paul Abbott, Kevin Appier, Shane Reynolds, Andy Ashby, Hideo Nomo, and Donovan Osbourne.

That's a total of 34 win shares - 15 from Flash. The problem isn't that they're not likely to age as well as the Big Unit or Jaime Moyer, but that only one or two of them has a chance to be as good as an aging Terry Mulholland. Obviously, they'll keep their lead at age 35, and I think their age 36 lead is safe, but after that I'm not sure that they'll do much better at all when everyone's done.

...um, so they're not aging better? Or just barely better? Let's look a little closer at the numbers and see what we find. Let's divide them all into decade-of-birth groups going back into the 1890s, the first decade where a large majority of pitchers were liveballers:

Age	1890s	1900s	1910s	1920s	1930s	1940s	1950s	1960s
20	15	1	7	6	12	12	9	7
21	27	14	13	21	22	27	26	14
22	41	26	20	23	38	38	39	33
23	50	33	33	40	50	67	60	57
24	72	51	56	60	69	80	77	73
25	93	68	85	71	88	90	91	100
26	94	88	100	87	100	100	100	97
27	95	93	75	100	99	92	94	90
28	97	100	91	98	85	83	86	96
29	100	94	94	90	97	82	82	97
30	96	91	92	88	86	73	72	88
31	87	89	79	81	94	59	60	82
32	66	77	66	66	64	59	56	72
33	70	68	70	61	55	41	46	59
34	58	55	60	52	46	37	36	50
35	44	43	47	42	29	30	28	46
36	30	39	34	30	21	26	23	42*
37	23	27	27	19	15	18	14	26*
38	16	28	18	12	11	13	8	22*
39	12	17	13	9	6	10	5	12*
40	8	10	5	6	5	10	4	12*

The 1960s have the earliest peak season. The things you learn when you dig through the data!

Occasionally, the information is a bit fluky. For example, there's no reason that I can tell for why the 1910s did so poorly at age 27. Sometimes the distribution of Win Shares within the prime is a bit random. Odds are that's why it's as low as a 75 there.

Looking at all the data, things are getting a bit more interesting. Current pitchers are aging much better than any recent ones as the previous 30 years' worth of pitchers aged far worse than any other liveballers. Just look at age 35 -- the 1930s-50s are all at/under 30% of their peak value. Everyone else is 42% at worst. Mighty stark contrast - - and a very unexpected one. I wouldn't have thought that a group of pitchers that combined to have 6 300-game winners, 3 other 280-game winners would be part of the era that aged poorly, but that's exactly what this says.

How d'ya explain that? Well, looking at their early 20's, they were worked harder than any other group, except maybe the 1890s. My guess is they were worked hard young, a disproportionate percentage of them hurt their arms and could not go on, but those that did could rack up the counting stats like no other group. Thus you can have the bad overall aging patterns exist alongside all Seavers, Blylevens, Suttons, Kaats, and Carltons.

Going back to the current pitchers, though they are aging better than the previous three groups, they are not aging better than the 1890s-1920s guys. Age 36 and 40 are the only ones they top, and when the 1968-9 guys are done, that may not even be the case.

Meanwhile, at age 33 and 34, they are worse than all those guys. What gives? With all the medical care, new surgical procedures, and anti-inflammatories this information doesn't make any sense.

Two issues are clouding the data, only one of which I can really adjust for. First, the one I can't adjust for, is WWII. This has a huge impact on some of the earlier groups. It doesn't impact the 1890s pitchers at all as they were all done by Pearl Harbor and only one - Hod Lisenbee - came back during it. Hod earned zero win shares in his 1945 return. No impact there.

The 1900s guys had a definite impact -- the war artificially inflated their Win Shares totals in their 30s. Several of these hurlers received a disproportionate share of their career value in their mid-to-late 30s, which not-so-coincidentally came during the war. Topping the list were Johnny Niggeling, Ed Heusser, Rip Sewell, all of whom earned over 50% of their value in these years. They were not alone as other, rather talented pitchers such as Claude Passeau, Bucky Walters, and Spud Chandler also earned around 1/3 of their career value over the same timeframe.

Perhaps some were legitimate late bloomers, but even if they were, the war excessively amplified their value in these years. Plus, there are still others, such as Boom-Boom Beck, who tied a career high for single season Win Shares in 1945 at age 40.

The impact on the next decade-group was even more drastic. Looking through the database, I searched for examples where a pitcher had been pitching prior to the war, lost some seasons, and then came back -- war-related lost years. I found 61 such seasons for the 76 pitchers in this group. Their average age: 29.1 years. The war reduced their prime, and thus made their production in their 30's a greater portion of their overall value than it would have been.

The impact is not nearly as strong on the 1920s pitchers. Many, such as Bob Lemon and Vic Raschi got a late start because of the war. Others, such as Warren Spahn, had lost seasons of their own. It isn't as easy to estimate time lost because every era has pitchers who don't start until age 26 or 27, or a guy who gets a cup of coffee at age 22 and does nothing for a while afterwards. The main impact would be that many guys had their careers delayed, and thus had their arms less-taxed in their early 20s. Given what happened to the 1930s-50s pitchers, that helped them a great deal.

Still, the experience of the 1890s pitchers shows that WWII can't be used to explain all of this. And there is one other factor - the way in which MLB got the service of minor leaguers. Here's a much simpler chart: a complete list of all pitchers who did not have any win shares prior to their age 30 season yet went on to start 100 games along with their actual year of birth:

1852 Ed Cushman		 64 WS
1886 Frank Miller	 56 WS

1893 Ray Kremer		141 WS
1895 Bob Smith		135 WS
1896 Heine Meine	 54 WS
1903 Curt Davis		165 WS
1903 Johnny Niggeling	 78 WS
1903 Jim Turner		 83 WS
1907 Rip Sewell		139 WS
1908 Bob Klinger	 64 WS
1911 Roger Wolff	 58 WS
1912 Mickey Haefner	 88 WS
1914 Ellis Kinder	145 WS

1922 Connie Johnson	 48 WS
1965 Masato Yoshii	 36 WS
1965 Orlando Hernandez	 62 WS

11 of the 16 pitchers were born within 21 years of each other. That's a curious bunching. Some are there because of WWII - Niggeling and Wolff are such pitchers. Most aren't, though. Curt Davis gained a little bit from WWII, but he'd have 100 GS Hitler or no Hitler. Ditto Rip Sewell. And the first few guys were done by the time the US entered the war. Something was up, and it wasn't necessarily the war.

Making the bunch-up even more interesting is the almost complete lack of such pitchers since then. Of the three post-Kinder'rs, one was a major league pitcher in Japan, one was a Cuban defector, and Connie Johnson was a black pitcher. Given that only 6 teams had integrated by Labor Day, 1953, I don't see his status as comparable to the turn-of-the-century gang.

What happened then? Let's look at the best pitcher in the bunch, Curt Davis. Prior to joining the Philllies, he spent six years pitching for the San Francisco Seals in the PCL, at which time that league was as good a minor league as the 20th century has ever had. Though he was not a standout right away, he did have a breakthrough season a few years before coming to the Phillies. Simply put, the turn-of-the-century guys were late bloomers who a generation earlier would've been overlooked entirely, and a generation later once the Branch Rickey minor league system had taken over, these men would've been spotted earlier and given their starts.

This I can try to adjust for - call it the Curt Davis Adjustment. Here's how the 1890s, 1900s, 1910s, 1920s, and 1960s look if you throw out all the pitchers with no win shares before their age 30 season:

	1890s	1900s	1910s	1920s	1960s
19	5	0.3	3	4	2
20	15	1	7	6	7
21	27	14	13	21	14
22	41	26	20	23	33
23	50	33	33	39	57
24	72	51	56	60	73
25	93	68	85	71	100
26	94	88	100	87	97
27	95	93	75	100	90
28	97	100	94	98	96
29	100	94	92	90	97
30	95	88	90	87	88
31	83	86	75	81	82
32	63	74	62	65	71
33	66	62	67	59	57
34	54	50	53	50	50
35	39	41	42	41	45
36	26	33	31	30	35	37*
37	21	21	24	19	23	29*
38	13	23	17	13	18	25*
39	12	14	10	9	8	13*
40	7	6	4	6	7	14*

First, the number directly in the 1960s column is what unadjusted. What I mean that 35 in the age 36 line means that what the pitchers born from 1960-8 did that year is 35% of what the pitchers born from 1960-9 did in their peak season. The incredible thing is that the ‘60s are already ahead of everyone at age 36, and almost there at age 37 even though they're only at 90% and 80% of their full roster in those years. The *'d columns are adjusted, and they're clocking everyone.

This is even more remarkable when you realize that there's still a WWII adjustment to be made to all but the 1890s. Though their lead is impressive, it can be overstated. Again, there's no real evidence that they age better until age 35. Also since there's no WWII adjustment for the 1890s guys, they make a good comparison for the 1960s. Assuming that the guys born in the late 1960s age as badly as it looks like they will, the children of the ‘60s, though they will age the best, won't be all that far in front of the men from the Gay ‘90s.

Could this be taken further and adjusted for people who only had 5 Win Shares before their age 30 season? That's tricky because the worst pitchers in the study can rack up a good deal of innings in 5 win shares or less. (Heck, Kevin Jarvis only has 12 win shares total in his career, but he's in the study). Maybe move the year back a bit to 27 or 28? I tried, and it doesn't change the results above. The 1960s have actually had more late bloomers than any recent decade-group. If you don't believe me just ask Paul Abbott or Mark Gardner or Steve Sparks.

Can I find an explanation for why they aged so well back in the days of populism, the Pullman strike, and the “glory days” of lynching? Here's a list of the 1890s pitchers who earned the most win shares from age 30 onward: Dazzy Vance, Dolf Luque, Eppa Rixey, Charlie Root, Urban Shocker, Burleigh Grimes, Sad Sam Jones, Stan Coveleski, Jesse Haines, and Rube Walberg.

The leader is possibly baseball's greatest late bloomer, and three are spitballers. These pitchers did age better than their peers - though frankly the Grandfathered-In Gang didn't age that much better than most liveballers (more on that later). Still, they do help the 1890s guys as a whole and thus the 1960s pitchers post-35 aging is that much better.

So much for that question - let's try a different one with the database: Are peak seasons changing. I'm a little leery of this breakdown. Normally I let Excel do the math for me, but I couldn't get it to sort horizontally, so I had to go through by hand and figure peak season. There's a greater chance for error here. Three groups: peak season for everyone born prior to 7/1/69; for all liveballers born before the 1960s, and then the 1960s group. Plus, off to the side a little chart saying what percentage of peak seasons are occurring when. Let's look at the results:

Age Total	Live	1960s		         All	Live
17 - 1		0	0		17-9     0.6     0.0
18 - 1		0	0		20-4    21.5	19.1
19 - 5		0	0		25-9    52.6	51.4
20 - 14		4	1		30-4    21.7	24.9
21 - 29		12	0		35+      3.7	 4.6
22 - 44		18	3
23 - 70		36	9
24 - 98		64	8		        1960s
25 - 137	65	29		18-9     0.0
26 - 145	85	22		20-4    12.9
27 - 126	75	12		25-9    55.2
28 - 108	68	13		30-4    23.9
29 - 109	68	14		35+      8.0
30 - 71		50	9
31 - 71		46	12
32 - 44		29	7
33 - 47		34	5
34 - 25		16	6
35 - 17		12	5
36 - 12		7	5
37 - 7		6	1
38 - 4		4	1
39 - 2		2	0
40 - 2		1	1
All - 1189	702	163

The only real news here is that current pitchers are far more likely to have a peak season in the latter half of their 30s. Also, no one is likely to break Kid McGill's record for the earliest peak ever.

Let's ask another question: Using the info available in the Neyer/James Guide to Pitchers, how do fastballers age compared to other groups of pitchers? Since liveballers age so much differently than dead-heads or box'rs, let's just look at liveballers born before the 60s to start with. The results (in parenthesis is the number of pitchers in each group):

	Fast	Junk
Age	(360)	(232)				Fast	Junk
18	1	0.3			16-19	0.5	0.2
19	4	2			20-24	17.5	11.9
20	9	6			25-29	42.1	39.6
21	25	13			30-34	29.4	31.9
22	34	25			35-39	8.9	13.5
23	51	40			40+	1.3	2.9
24	74	52
25	86	78			16-27	43.7	34.4
26	100	89			28-49	56.3	65.6
27	97	91
28	92	99
29	88	100
30	83	93
31	73	79
32	65	74
33	58	65
34	45	58
35	31	53
36	26	38
37	18	28
38	14	21
39	9	16
40	6	11
41	4	8
42	3	5
43	1	3

What the heck? This is perhaps the most remarkable breakdown yet. Not only do fastballers peak and prime earlier, and junkballers age better, but just look at how both columns go. In both cases, each group of pitchers get better every year until their peak and then get worse every year after it. Fastballers are ahead every year until age 27 and then are behind every year from that point on.

Let's break it down by four major pitching groups - fastball, curveball, slider, and sinker. Does one group just warp things or what?

	Fast	Curve        Sliders   Sinker
Age	(360)   (109)          (38)    (34)
19	4	1	         0
20	9	7	       0.2	11
21	25	14	        5	23
22	34	29		15	33
23	51	42		29	61
24	74	57		46	61
25	86	83		75	84
26	100	94		88	89
27	97	96		86	83
28	92	99		84	93
29	88	100		100	100
30	83	91		74	84
31	73	77		58	61
33	58	64		46	42
34	45	57		48	35
35	31	51		36	33
36	26	31		22	34
37	18	23		12	20
38	14	19		6	16
39	9	10		4	13
40	6	7		3	7
41	4	6		5	1
42	3	2		4	0
43	1	1		1	0

A few things - first off, all junkers peak at the same time. Neat. Curveballers do seem to age the best, but there is a problem - especially with the slider group. Their peak season is unusually peak-arific. There's no other season over 90. That sets off my danger detector. There's a problem in looking at pitchers as I'm doing here - assigning a year's Win Shares by peak. Though this system has the benefit of making the results easier to quickly read and comprehend to the gentle reader at home, if the peak is excess, it artificially deflates all other seasons. Normally this isn't an issue so I go with it, but with sliders it's an issue. Let's onto a different chart - % of overall value in given eras.

Ages	 Fast Curve    Slider	Sinker
16-19	4.7	1.3	0.05	0
20-24	17.5	13.2	10.4	17.8
25-29	42.1	41.9	47.3	42.6
30-34	29.4	31.6	32.2	27.9
35-39	8.9	11.9	8.7	11.0
40+	1.3	1.4	1.4	0.7

Curvers seemed to age better, but for a while at least sliders aged the best. In general, these confirms that no single group distorts the picture. Fastballers can't blame their poor comparison on knucklers or grandfathered-in spitballers, or just one group of junkers. The best they can claim here is a slight lead over sinkers in the early 30s, and a barely-there lead over sliders in their late 30s. Yippee.

That breakdown is so clear, you can pretty much assume that you will see something similar for the 1960s guys. Let's check anyway. And since I got them, let's look at the guy born from 1970-4 as well. Here it is:

           1960s		   1970-4
	Fast	Junk		Fast	Junk
Age	(111)	(33)		(38)	(11)
19	0.4	1		0	0
20	4	7		2	3
21	12	15		8	16
22	32	31		19	35
23	57	48		45	52
24	70	71		63	80
25	98	100		84	85
26	97	73		91	100
27	90	66		100	80
28	94	91		88	79
29	100	90		70	63
30	87	71		62	50
31	83	57
32	71	58	Ages	Fast	Junk
33	58	36	16-9	0	0
34	53	24	20-24	18.5	25.2
35	45	31	25-9	58.6	55.2
			30+	22.9	19.6

	Fast	Junk
16-9	0.04	0.1
20-4	15.2	18.8
25-9	41.8	45.7
30-4	30.8	26.9
35+	12.2	8.5

So, just to confirm, the clearest and most consistent aging pattern split that I've come across for liveball pitchers, just completely stopped, came to an end, and totally reversed itself, oh, about 20 years ago or so. Sure, why not. Now junkers get up to speed quicker, peak and primer earlier, and age worse. Makes perfect sense? OK, maybe there's a simple solution. That liveballer cluster covers a lot of years. Maybe it began as wildly pro-speedballers in way back in the days of Ruth and has gradually shifted. OK, I like that theory. Let's check on the pitchers born in the 1950s and 1940s as separate groups. Maybe, hopefully, they'll show a similar pattern to the 1960s.

	1950s					1940s
Ages 	Fast	Junk			Ages	Fast     Junk
16-9	0.1	0.2			16-9	0.8	0.5
20-4	20.6	17.5			20-4	21.6	18.7
25-9	45.3	44.4			25-9	43.8	38.8
30-4	26.7	27.5			30-4	23.9	25.8
35-9	6.7	9.0			35-9	7.8	12.1
40+	0.6	1.4			40+	2.1	4.1
Prime	24-8	25-9			Prime	24-8    25-9
Peak	26	25			Peak	26	29

Not what I wanted to see. It's the same pattern that persisted throughout the liveball era. Yes, junkers had an earlier peak by one year in the 1950s, but look at all the other info. The early peak looks like a fluke. Whatever happened to the 1960s/70s pitchers, it came out of nowhere.

Let's go backwards now. Maybe I can find some clues if I look at deadballers and pitchers box guys. Here they are:

Deadballers					pre 1893
Ages	Fast	Junk			Ages	Fast     Junk
16-9	1.1	0.2			16-9	3.2	2.5
20-4	26.5	20.2			20-4	42.7	37.1
25-9	44.3	49.6			25-9	36.1	45.9
30-4	20.3	25.6			30-4	15.5	13.6
35-9	5.9	4.0			35+	2.6	0.9
40+	1.8	0.4			Prime	21-5    23-7
Prime	24-8	25-9			Peak	23	27
Peak	25	27

Well, this looks a little familiar. Fastballers do better early? Check. Earlier prime? Check. Earlier peak? Check. Do they do worse after age 30? Well, it gets a little confusing here, but the fastballers are doing worse in their early 30s in the deadball era. So in the first phase of decline they're still worse. As for the box'rs, what you have to remember is just how wildly early these guys as a whole peaked. Remember they were declining in their late 20s, and again in the first phase of their decline, fastballers are doing poorly.

So just to recap - from 1876 to the 1980s baseball went many changes - the pitchers were moved back twice, given a mound, lost the spitball and shineball, had several eras of high- scoring offense, and low-scoring deadness. It survived two world wars and other, smaller conflicts. It integrated, adopted night baseball, conquered the minor leagues, went to airline travel, coast-to-coast leagues, and paid grown men to put on silly looking costumes and serve as mascots. Yet throughout all this turmoil, one consistent held true: fastballers started earlier, got up to speed quicker, entered their prime earlier, peaked earlier, and - through at least the first stages of decline - performed considerably worse than junkers.

Then came the 1980s. Now absolutely none of that is true. The exact opposite is going on. Sure. OK. Why not? What the hell.

Ideas? Explanations? I'm empty folks. Not a clue. I can throw a few things out - the 1980s is associated with the rise of the split-fingered fastball. Does that have something to do with it? I dunno. Pitch counts? (shrugs). Maybe. You know what though? None of these really explains it because there are two separate things going on - not only are fastballers aging better, but everyone else is aging worse. How the heck does the rise of the splitter cause curveballers to pitch worse at age 34? It's the damnedest thing.

So much for that one. Next question -- what happens when you compare how righties and southpaws age? First, let's look at liveballers born before 1960:

RIGHTYS VS. LEFTYS
	R	L	R	L
19	3	3	0.3% 	0.3%
20	8	9	0.7%	0.8%
21	21	20	1.8%	1.9%
22	32	32	2.7%	3.0%
23	52	44	4.3%	4.1%
24	72	60	6.1%	5.6%
25	91	76	7.6%	7.1%
26	99.5	100	8.3%	9.4%
27	99.9	92	8.4%	8.6%
28	100	88	8.4%	8.3%
29	99	88	8.3%	8.2%
30	93	84	7.8%	7.8%
31	87	73	7.3%	6.8%
32	71	68	5.9%	6.4%
33	64	57	5.4%	5.3%
34	54	48	4.5%	4.5%
35	43	36	3.6%	3.4%
36	32	29	2.7%	2.8%
37	23	20	1.9%	1.9%
38	17	16	1.4%	1.5%
39	13	10	1.1%	0.9%
40	9	6	0.8%	0.6%
41	6	4	0.5%	0.4%
42	4	3	0.3%	0.3%
43	2	1	0.2%	0.1%

This is one instance where the peak seasons distort the comparison. The lefties had one big year with only one other season (barely) worth 90% of it. The righties had their top four seasons within 1% of their value. Maybe there's a reason why one group has such a cluster of peak seasons and the other doesn't, but I'm not assume that's the case. As mentioned earlier, at times the distribution of win shares within the prime is a bit fluky.

That's why I have the second series of columns on the right. That's what percentage of the pitchers' total win shares were accumulated during that one season. The lefties gained a considerably greater percentage in their best season than the righties ever did, and that skews that data in the left columns. According to those columns, the righties smoke the lefties in terms of aging. Looking at the columns on the right, it's quite a bit closer. Looking at it another way:

	Liveballers
Ages	R		L
16-19	0.3%		0.3%
20-24	15.5%		15.5%
25-29	41.0%		41.5%
30-34	30.9%		31.1%
35-39	10.7%		10.4%
40+	2.1%		1.5%

16-27	40.2%		40.8%
28-49	59.8%		59.2%

A very modest, and probably insignificant lead for righties. They have less an advantage of less than 1%.

Has this always been true? Let's look at deadballers, and then pitchers box guys:

Lefties - Deadball
	R	L
19	6	3
20	15	21
21	26	25
22	45	55
23	58	73
24	79	89
25	97	87
26	97	99
27	100	100
28	99	87
29	87	72
30	73	58
31	60	38
32	48	27
33	37	19
34	25	17
35	17	12
36	12	9
37	9	4
38	7	2
39	3	5
40	4	3
41	3	1
42	2	0
43	1	0

	Deadballers
Ages	R		L
16-19	0.8%		0.3%
20-24	22.1%		29.0%
25-29	47.5%		49.0%
30-34	24.0%		17.6%
35-39	4.7%		3.5%
40+	0.6%		1.5%

16-27	51.9%		60.9%
28-49	48.1%		39.1%

Box	R		L
16-29	85.0%		92.2%
30+	15.0%		7.8

Well that's interesting. Clearly before the liveball era lefties aged worse, and not just bit a little bit worse. They began falling apart as soon as they passed their peak and generally aged a year or two worse than righties. And this was true for the entire half-century of ball back then.

So if that's the case, are modern lefties and righties aging the same or has the balance slowing been tipping toward lefties? Let's look at the 1960s and 1950s pitchers:

	1960s
Age	R	L
16-9	0.2	0.1
20-4	16.4	14.8
25-9	42.4	39.0
30-4	31.0	28.6
35+	9.9	17.5
Peak	25	26
Prime	25-9	26-30

	1950s
Age	R	L
16-9	0.1	0.3
20-4	19.9	22.4
25-9	44.0	45.1
30-4	26.6	25.9
35-9	8.3	6.0
40+	1.1	0.3
Peak	26	26
Prime	25-9	25-9

	1940s
Age	R	L
16-19	0.8	0.3
20-24	22.3	17.8
25-29	43.2	38.2
30-34	22.3	30.7
35-39	8.5	10.8
40+	2.8	2.3

Some conflicting data here. The 1960s lefties are smoking the righties, especially in old age. Take a bow Jaime Moyer, Chuck Finley, David Wells and Randy Johnson. A similar trend occurs in the 1940s bunch. Though righties did better after turning 40, they were torched in the previous ten years. Meanwhile there's the 1950s, where there is little difference at all, but a minimal edge to righties during the decline years.

What to make of this? Lacking the desire to sort through every decade of pitchers, here's my theory: throughout the deadball era righties (obviously) aged better, but this trend slowly reversed itself. At first, righties likely had a small edge. Actually, given the above charts on pitchers since 1940 and combining it with the overall liveball info, righties must have aged better in the initial decades of the liveball era. For whatever reason - I'll try to take some guesses later - this has flipped over. So why were the 1950s backwards? They don't fit the trend. I have no idea, but keep in mind the sample size for one decade isn't as large - especially if you're only looking at lefties born each decade. Maybe it just a dry spell for lefthanded pitchers. It could be as simple as that?

OK, so why have lefties improved their aging patterns? One theory came to me as I looked at the 1960s lefties: call it the Terry Mulholland Theory. As anyone who has seen baseball in recent years can attest, teams often like having a lefty in the ‘pen. Some, like Jesse Orosco, can seemingly pitch forever as a LOOGY if they can exhibit some minimal control.

That's a theory, but I don't buy it. Sure LOOGYs are prolific, but there ain't many that are this study. Captain LOOGY himself, Orosco, fell 96 starts shy of making it. There are some starters-turned-relievers in the study - Mulholland, Rheal Cormier, Chris Hammond, Jeff Fassero, and Kent Mercker are the big ones from the 1960s - but not many. The previously mentioned guys are about it for that decade. And their contributions pale in comparison to Glavine, Johnson, Wells, Moyer, & Rogers. Besides, their contributions are largely matched by that of righty converted starters like John Smoltz, Flash Gordon, and Cal Eldred. Lefties do have some advantage there, but not enough to explain the bid difference in the 1960s group.

So what is it? Damned if I know. That's my own good theory. I wish I had a brilliant answer right about now, but I don't. Ah well - let's ask another question: What about knucklers? Do they age the same? They have a reputation as late bloomers. Let's check it out - comparing pitchers listed as primarily knucklers in the Neyer/James Guide to my main sample of liveballers:

     KNUCKLE	       LIVE
20	0		8
21	3		21
22	15		32
23	35		50
24	56		69
25	76		86
26	72		100
27	49		98
28	80		97
29	89		96
30	100		79
31	92		70
32	99		57
33	77		48
34	88		39
35	75		31
36	67		23
37	51		16
38	42		12
39	42		8
40	31		6
41	18		4
42	15		2
43	13		1
44	7		1

Knucklers have the latest prime (ages 28-32) of any group that I've isolated almost without exception. Pitchers who got their first real chance at age 29 or later had a later prime, but that's in. Pitchers who got started at age 28 had the prime (I'll discuss this stuff more later on), and that's a group which by definition should have had a late start. Nothing terribly surprising, but it's nice to have the data.

Well, that's knucklers, what about spitballers? There's another group that should age better. This is a bit more confusing, because most were deadballers, but there are also some grandfathered-in guys. Since live and deadball eras had such different aging patterns I'll compare grandfathered guys (referred to people as “Last”) to liveballers, and deadball spitters (D.Spit below) to other deadballers. Making it even more confusing is Jack Quinn, who pitched most of his career in the liveball era, but pitched more innings in the deadball era than most of the deadballers in this study. I'm actually going to include him in both groups for now. Here are the results:

Age	Last	Live	D.Spit	Oth.Dead
20	0	8	0	19
21	8	21	11	28
22	20	32	22	51		Ages	D-Spit	noQuinn
23	37	50	39	65		16-9   0%	 0
24	47	69	49	85		20-4   14.3	15.4
25	73	86	71	97		25-9   49.2	52.2
26	92	100	77	100		30-4   27.6	28.5
27	100	98	100	98		35-9   5.6	3.6
28	72	97	85	95		40+ 	3.3	0.3
29	78	96	81	82
30	81	79	73	68		Dead - Others
31	71	70	68	51		16-9	0.8%
32	67	57	45	42		20-4	24.9
33	48	48	23	34		25-9	47.2
34	37	39	23	22		30-4	21.7
35	42	32	22	15		35-9	4.5
36	39	23	15	11		40+	0.9
37	21	17	5	9
38	16	12	4	6		Last	 Live
39	17	8	4	4	30-4	26.0	31.0
40	17	6	6	4	35+	22.0	12.3
41	9	4	2	3
42	10	2	3	2
43	9	1	4	0.7
44	10	1	4	0.2

Several things - first, no one quite matches the record of knucklers. These guys did age better, but not that much better. Second, please note that the deadball spitters have an unusually large peak season which artificially depresses all their numbers. If you look at the main chart isn't entirely clear that they aged better than other deadballers. But look at the smaller charts on the right. Deadball spitters had 36.5% of their overall value after the age of 30. Other deadballers weigh in at 27.1%. Considerable advantage to the unsanitary stylists. Even if you toss Quinn out it doesn't change that much as his impact is almost entirely limited to age 40 and beyond (though his impact is immense from that point onward). The grandfathered guys had a much more modest advantage - 48% of their career value after turning 30 instead of 42.3%. This advantage doesn't really appear until after age 35.

This helps solve the riddle of 1890s pitchers. This was the gang that aged so well in their late 30s despite having no WWII impact. Well, this spitter split does prove that the grandfathered guys born in the McKinley era did boost the overall aging patterns.

Well, spitters age better. No big surprise there, but again, it's always nice to have the data. Any thing else worth checking? Well, how about walk rates and strikeout rates? Do pitchers with better K-rates age better? Do pitchers with better control age better? And how do flamethrowers compare to control masters in terms of aging?

Fortunately, due to the thankless yeomen work of Dr. Memory, this is pretty easy to answer. He, for whatever masochistic reasons of his own, went through the statistical record and adjusted the K-rates, W-rates, and K/W ratios for every pitcher in this study for their leagues' rates With these league-normalized numbers, it's easy to compare pitchers across eras.

Again, let's look at the main sampling of liveballers born before 1960 and see what happens. For this, I've divided up all pitchers into 10 groups - from the best strikeout pitchers, to the worst strikeout pitchers, and the same with adjusted BB rate. Let's look at the results, starting with K-rates. The info at the end is average career Win Shares per pitcher in the group, and at the very end the Dr. Memory K #s of the pitchers in each group:

Adj. K-rate
Grp     16-9	20-4	 25-9	30-4	35-9	40+	Peak	Prime	Avg  	 K#
A	0.7	15.2	38.5	29.5	13.5	2.7	27	26-30	160.8	124+
B	0.3	20.0	40.4	27.7	10.4	0.9	26	25-29	120.7	113-23
C	0.4	20.1	41.0	29.6	7.9	1.0	29	25-29	128.1	107-12
D	0.5	15.3	39.8	31.4	9.9	2.9	29	26-30	120.0	101-06
E	0.3	15.5	42.9	29.7	9.6	2.0	26	26-30	120.5	95-100
F	0.4	13.9	41.1	30.0	11.2	3.4	27	26-30	103.8	90-94
G	0.4	21.9	42.1	27.9	6.6	1.1	25	25-29	99.1	86-9
H	0.4	11.3	44.2	34.8	9.1	0.6	29	26-30	91.5	80-5
I	0  	12.5	39.7	31.6	14.0	2.2	26	26-30	104.3	73-9
J	0.1	17.0	46.5	28.2	8.1	0.2	28	25-29	83.5	72-

First off, it does appear that being a great strikeout pitcher comes in handy when aging, but not nearly as handy as I would have guessed. Group A had 45.7% of their value after age 30, which is definitely above-average as half the groups had less than 42% of their value from that point onward. They are not, surprisingly, the best aging group. That honor goes to, shockingly, the Group I, who has 47.8% of their value after age 30. The runner up group is far closer to the fifth best aging group than to them.

This I find very surprising because in the New Historical Abstract Bill James shows that the best indicator of future value for a young pitcher is his K-rate. He mentions that the last young right-handed pitcher with a consistently poor K-rate who ended up having a good career was Lew Burdette almost a half-century ago. So why the difference here?

Simple - we're looking at career K-rates, not just those of young'uns. Almost everyone has their K-rate go down as they get older, and so career K-rates really aren't a great measure of a pitcher's ability to age well. In fact, though Group A has the 2nd best aging pattern, groups B and C have some of the worst aging patterns. Both of those groups used up over 60% of their value by the time they reached 30 years of age.

There is still some evidence here to bolster the importance of K-rates Group J, for example, has one of the worst aging patterns. They're the worst after age 40, and 2nd worst to K-rate group G after age 30. The results are decidedly mixed, though.

How about walk rates?

Adj BB-rate
Grp	16-9	20-4	25-9	30-4	35-9	40+	Peak	Prime	Avg	BB#
A	0.1	13.4	39.1	31.9	12.8	2.7	30	26-30	144.7	144+
B	0.7	14.2	38.4	31.1	13.0	2.6	28	26-30	148.0	130-43
C	0.05	17.6	36.3	29.9	13.8	2.2	26	25-29	137.0	121-9
D	0.8	11.6	43.4	34.1	8.7	1.4	29	26-30	120.0	115-20
E	0.1	12.0	36.5	34.7	13.9	2.8	30	26-30	121.1	108-14
F	0.2	14.4	39.9	31.0	12.3	2.3	29	26-30	105.6	103-7
G	0.2	15.4	43.2	31.9	8.7	0.5	27	26-30	113.8	98-102
H	1.0	19.7	50.5	24.2	4.1	0.5	26	25-29	86.1	92-7
I	0.2	20.5	42.9	28.1	7.1	1.2	26	25-29	84.8	82-91
J	0.05	23.5	50.5	20.1	4.0	2.0	27	25-29	67.5	81-

The first thing I notice is how much better the BB#s are in comparison to the K#s. They don't fall below 100 until group G here, while they fell below with Group E up above. These pitchers on the whole had better control than strikeouts. Interesting.

What's even more important here is that career W rate seems to have a clearer impact on aging patterns than K-rates do. Group A has the 2nd best aging pattern (which I'm arbitrarily defining as what percentage of their overall value did they get after age 30). So far that's just like the K-rates, but here Group B has the 3rd best aging pattern. Group C has the 4th best aging pattern. The groups with 6 best BB numbers have the 6 best aging patterns. The three worst aging patterns were (by far) the three bottom groups. There's also a broader range. In the K rates, the group with the greatest overall value after age 30 was at 45.7%. Here, four groups best that mark and a fifth comes in at 45.6%. The lowest amount of post-30 value with the K-rates was 35.6%. Here, there are two groups (H and J) under 30%.

The best aging group here, if you're wondering, is Group E at 51.4%. I have no idea why they lead, but there it is. Group J came in dead last, with barely a quarter of their value coming after turning 30.

One other thing comes out in this: ages 26-9 clearly are the main prime years for liveballers. Despite the fact there is such a notable difference in aging patterns, the prime years are almost the same for all. Some begin their prime a year earlier than others, that's the only difference.

Whadaya say we compare K-rates to W-rates? I've got the chart figured out, but really, it doesn't add anything. It'll just repeat what I just said. Instead, let's move on to the last of the Dr. Memory info: what impact does a K/W ratio have on a pitcher's aging pattern?

Adj K/BB-ratio
Grp	16-9	20-4	 25-9	30-4	35-9	40+	Peak	Prime	Avg	K/BB#
A	0.8	13.8	35.9	31.3	14.8	3.4	30	26-30	188.8	139+
B	0.1	12.2	36.7	33.4	14.2	3.5	26	25-29	151.4	125-38
C	0.7	19.0	40.4	29.9	8.9	1.1	29	26-30	139.9	115-24
D	0.2	1.8	42.0	30.8	12.3	2.9	26	26-30	132.3	107-14
E	0.1	18.1	41.5	30.8	8.3	1.1	29	25-29	104.9	101-6
F	0.3	14.2	42.9	32.1	9.6	0.9	28	26-30	100.7	95-100
G	0.4	16.9	46.6	28.8	7.2	0.2	26	25-29	94.3	91-4
H	0.1	17.4	43.5	30.5	7.0	1.5	26	25-29	93.0	84-90
I	0	19.9	43.7	25.7	9.6	1.0	26	24-28	69.5	77-83
J	0.1	19.5	51.1	25.2	4.2	0	26	25-29	53.8	76-

From the Dept. of Not At All Surprising Info: better pitchers tend to have better K/BB ratios. It's perfect the way it works out -- the best K/BB group has best average win shares, group B in second and so on down the line to group J with the worst average. The most interesting thing to me is that the better the group of pitchers, the later the prime. It's not perfect as Group B had an earlier prime than C, D, and F while averaging more win shares per pitcher, but that's the only major exception. Pitchers with a lousy ratio, when they start declining and losing a little of what they had, aren't long for this game. Guys in Group J get barely more of their value after age 35 than Groups A and B get at after age 40.

Another question: what about when guys first make their mark in the baseball? Do guys who come to the bigs at an early age have the same aging pattern as guys who come in later? For this study, I'm not looking at how old a pitcher was when he first arrived in MLB but how old he was when he first earned 3 win shares in a season. There's just too many guys who came up for a cup of coffee and then didn't come back for another year or three. This has been an old story from Joe Nuxhall to Mike Morgan. By making it three win shares instead I'm looking at how old they were when they first got themselves somewhat established. The first group is 19 or younger (19-) and the last group is 29+; every other group is just one age. Here's the results (again looking at liveballers born before 7/1/59):

First Year with 3 Win Shares
Age 	19-	20	21	22	23	24	25	26	27	28	29+
18	9	1	0.4	0.1	0.2	0	0	0	0	0	0
19	56	2	0.3	0.1	0	0	0	0	0	0.4	0
20	66	57	4	0.4	0.5	0.2	0	0	0	0	0
21	78	77	76	3	1	0.5	0.2	0.3	0.3	0	0.3
22	84	74	72	73	4	1	0.2	1	0	0.4	0
23	80	72	88	88	67	4	1	0.4	0	1	0
24	88	94	98	100	79	87	4	2	0	0.4	1
25	82	100	99	99	91	96	82	3	2	1	1
26	87	76	100	94	100	100	100	92	2	1	0.3
27	100	82	91	82	85	91	96	99	76	7	4
28	89	71	77	80	82	85	86	99	90	100	1
29	73	73	64	75	83	86	91	100	100	89	43
30	66	64	54	67	66	88	90	98	99	97	68
31	47	46	49	56	54	76	75	91	99.7	97	82
32	37	52	44	52	52	61	67	72	94	74	86
33	28	43	38	44	44	53	64	56	87	76	100
34	29	34	34	35	38	40	45	49	82	73	94
35	20	22	26	27	28	40	38	36	40	57	78
36	18	15	20	18	24	22	31	31	40	52	60
37	7	13	15	13	14	12	26	17	30	40	49
38	8	6	12	7	12	5	18	15	20	32	48
39	1	3	9	8	6	1	18	11	11	19	36

Comments time: The 19- pitchers averaged more win shares than any other group, which makes sense. The best players should be the first to make it to the majors. However, looking at it here, they aged the worst from age 32-onward of any group here. That's interesting. This doesn't surprise me much. One of the favorite lists I ever cooked up was a list of liveballers who won 150 games before they turned 30. Only one - Greg Maddux - made it to 300. The others either: 1) had their arms fall off in their early 30s (Drysdale, Ferrell, Newhouser, Hunter, Holtzman), or 2) survived, but weren't nearly as good as they had been when they were young (Feller, Harder, Blue, Gooden). They had 52 20-win seasons before age 30, but only 4 afterwards, and 3 of those were Jim Palmer. The point: pitchers that were worked the hardest when they were youngest don't hold up the best when they age. That's exactly what happened here.

Another interesting result is that the peak often occurs at the same dang time. One question I had going in was would pitchers that came up later have the same aging curve as others, just begun later? In other words, would it take most of these groups the amount of time to reach their peak and prime? I don't see that happening in these results. Those that first established themselves from ages 20-25 peaked at about the same time - age 25 or 26. Only the age 22 pitchers missed out on that. Five of the first six groups all had their prime at either ages 23-7 or 24-8 (age 23 had their prime from 25-9). There are, obviously some differences, as guys who came up at age 28 peaked later than guys who came up at age 20, but whereas the early arrivals had a couple years to work up to their peak, the later arrivals often began in their peak. Ages 24-8 all began their prime either their first big year or the year after while only one of the earlier groups could say that.

It's also interesting to compare the latter groups to knuckleball pitchers. Knucklers aged better than just about all of them. Comparing their aging patterns to Groups 19- to 28 (I'll look at the 29+rs separately in a second) knucklers score the best at every age after turning 30 except age 31, where they finish third, and age 33, where they come in second. Every other year they best every last one of those groups. That's impressive. Comparing them to the 29+ group, they don't do quite as well, but they still do age better. Here's comparing those two groups from age 30-9:

Age	Knuck		29+
30	100		68
31	92		82
32	99		86
33	77		100
34	88		94
35	75		78
36	67		60
37	51		49
38	42		48
39	42		36

The 29+rs had the lead in the heart of their prime (33-35) and a narrow lead at age 38, but that's it. If anyone should age really good, it's guys who had accomplished nothing in MLB by age 29 yet still managed to start games. Yet knucklers aged a little better. This is despite the fact that there are several knucklers in the age 29+ group, including at least 3 pitchers who had no career win shares before their age 30 season.

One last bit I want to check. I've ignored everyone born after 6/30/69 here so far, and there are numerous guys from the first half of the 1970's who have 100 starts and have finished what should be their prime. Let's see how their aging. For comparison I'll line up their numbers against 1960s pitchers.

1970-4 Pitchers (58 pitchers)
Age    70-4	60s
19 	0	2
20 	2	7
21 	12	14
22 	24	33
23 	51	57
24 	67	73
25 	86	100
26 	93	97
27 	100	90
28  	97	96
29  	84	97
30 	71	88

I need to note that there are pitchers out there born from 1970-4 who haven't yet started 100 games but will end up doing so before their done, so those numbers aren't in stone. Obviously, the second half of the decade still has to go through the prime. As it stands, they're on track for the oldest peak season for any decade group since the 1920s, and the worst age 30 season of the liveball era. Again, this should change as some late bloomers emerge.