Babe Ruth's aging vs. Barry Bonds' aging

I recently read the book Cooperstown Confidential by Zev Chafets. 

On pages 184-185 it has

"Cole and Stigler (two academics) pointed out that Babe Ruth hit 198 homers in the last six years of his twenty-two year career, 28 percent of his career total of dingers. In the last six years of his career, Barry Bonds hit 195, or 26 percent. "There is no convincing way," the study said, "to demonstrate that Bonds' performance owed to drugs more than Ruth's did to his prodigious use of alcohol and tobacco." Which, of course, was nothing."

The first problem is that the last six years of Bonds' career were the years 2002-2007. That leaves out his 73 home runs in 2001 (all stats I present here come from Baseball Reference).

If we go by the last 7 years of his career, Bonds hit 268 home runs. That is 35.17% of his career total (268/762 = .3517). For Ruth, in the last 7 years of his career, he hit 244 home runs or 34.17% of his career total (244/714 = .3417).

This is still close, but Bonds has over taken Ruth just with this one adjustment.

Now Ruth did not hit many home runs before age 24 because he was mainly a pitcher early in his career. This holds down his career total. Other wise, he would have larger denominator and therefore an even lower percentage for his last 7 years.

I don't know how the numbers would change. Those early years in Ruth's career were part of the dead ball era, so even if he had been a full-time outfielder from ages 20-23, it might not have been many HRs.

But, from age 24 until the end of his career, Ruth his 694 HRs. So 244/694 = .3516. In his last 7 years, Ruth his 35.16% of his age 24-40 HRs.

What about Bonds? Bonds hit 697 HRs from age 24-42 (the end of his career). So 268/697 = .3845. In his last 7 years, Bonds his 38.45% of his age 24-42 HRs. The gap in favor of Bonds has grown a bit. But they are still close

One thing that holds Bonds' HR totals in his last 7 years were all the walks he got. He drew 1,011 walks in those 7 years including a record 232 in 2002, of which 120 were intentional (the most walks Ruth ever had in one season was 170).

In Ruth's last 7 seasons, he drew 704 walks. So Bonds has an extra 307. That is 307 times he had less of a chance or no chance to hit a HR. 368 of Bonds' 1011 walks were intentional. Baseball Reference shows 26 for Ruth, but I am not sure how much we know about IBBs in those years.

But just to have an idea of how much the extra walks mattered, with 368 being intentional and Bonds having .112 HRs per AB in his last 7 years, that projects to an extra 41 HRs. Even we use the gap of 307 walks, that would be an extra 34 HRs.

What this suggest to me is we should look at HR%. The table below shows Bonds' HR% each year from age 24-39 along with the league average. The last column is his relative HR% or his HR% divided by the league average.

Bonds' Age	HR%	Lg HR%	Rel HR%
24	0.0328	0.0207	1.5795
25	0.0636	0.0231	2.7577
26	0.0490	0.0219	2.2407
27	0.0719	0.0192	3.7449
28	0.0853	0.0252	3.3810
29	0.0946	0.0278	3.4015
30	0.0652	0.0278	2.3491
31	0.0812	0.0286	2.8437
32	0.0752	0.0280	2.6837
33	0.0670	0.0289	2.3179
34	0.0958	0.0325	2.9468
35	0.1021	0.0339	3.0147
36	0.1534	0.0335	4.5769
37	0.1141	0.0296	3.8617
38	0.1154	0.0306	3.7677
39	0.1206	0.0321	3.7567

You can clearly see something happen at age 36 (and perhaps as early as age 34). His Rel HR% jumps from 3.01 at age 35 to 4.57 at age 36, by far the highest of his career. After 5 years in a row with a Rel HR% under 3 from ages 30-34 (and well below 3 in 4 of those years), it starts rising slightly. But even after the very large increase at age 36, his Rel HR% from ages 37-39 are all very high. The only year before age 36 in their range was when he was 27.

The Giants play in what is now called Oracle Park. It opened in the year 2000 when Bonds was 35. The RF wall is 24 feet high. It was only 309 feet down the line when Bonds played but right-center field was 421. So it is not an easy place for a lefty (which Bonds was) to hit a HR.

From Bill James Handbooks, the HR rating for the park for lefties in 2001 was 57, meaning lefties had a HR rate of only 57% of what it was in the rest of the parks in the league. Over the years 2002-04 it was 75. The years 2001-04 cover the years when Bonds was 36-39 years old.

So Bonds still had this great HR% surge despite hitting in a tough park for lefties.

Now the same table for Ruth

Ruth's Age	HR%	Lg HR%	Rel HR%
24	0.0671	0.0064	10.4577
25	0.1179	0.0088	13.4142
26	0.1093	0.0111	9.8026
27	0.0862	0.0124	6.9452
28	0.0785	0.0105	7.4663
29	0.0870	0.0094	9.2487
30	0.0696	0.0125	5.5623
31	0.0949	0.0102	9.3501
32	0.1111	0.0104	10.6598
33	0.1007	0.0115	8.7906
34	0.0922	0.0141	6.5350
35	0.0946	0.0157	6.0268
36	0.0861	0.0132	6.5314
37	0.0897	0.0163	5.5097
38	0.0741	0.0142	5.2063
39	0.0603	0.0160	3.7609

I don't put much stock in those sky high Rel HR%s when he was younger. The dead ball era had just ended and maybe not many other guys had figured out how to hit like Ruth to generate so many HRs (or maybe they were still being conservative and swinging for line drives-it might not be easy to change batting styles very quickly). That would make the league average HR% pretty low and boost Ruth's Rel HR%.

But look at Ruth when he was 32 (that was 1927 when he hit 60 HRs). His Rel HR% was 10.65. But then it dropped 3 straight years with a slight increase at age 36 (but a far lower increase than Bonds saw at age 36). Then it falls quite a bit over ages 37-39. Those years are well below what it was for ages 31-33. But for Bonds, his Rel HR%s from ages 37-39 are much higher than for ages 31-33.

Bonds' Rel HR%'s from age 37-39 are very high compared to most of his career while for Ruth they are pretty low compared to his earlier years.

So it looks like Bonds had an unusual aging pattern in his late 30s. Perhaps very unusual.