Babe Ruth's aging vs. Barry Bonds' aging, Part 2

Click here to read Part 1.

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."

In this post I will look at how slugging percentage relative to the league average (Rel SLG) changed as both Ruth and Bonds aged.

This graph shows the Rel SLG for each of them from age 24-39.

It is pretty easy to see the difference. Up until age 36, Ruth is almost always higher than Bonds in Rel SLG. Even when Ruth is not ahead it looks about the same or Bonds is only ahead slightly.

But from 36-39, Bonds is well ahead of Ruth. Bonds goes up noticeably at age 35 and then has a very large increase at age 36. Ruth in those years is generally going down.

This table has the data.

Age	Bonds Rel SLG	Ruth Rel SLG
24	1.167	1.830
25	1.475	2.189
26	1.378	2.074
27	1.696	1.688
28	1.697	1.969
29	1.559	1.861
30	1.414	1.331
31	1.507	1.880
32	1.427	1.935
33	1.485	1.786
34	1.438	1.713
35	1.593	1.739
36	2.031	1.768
37	1.949	1.636
38	1.796	1.492
39	1.920	1.346

At age 35, Bonds goes up .154 (1.593 - 1.438) much more than Ruth, .026. Then at age 36 Bonds goes up .438 while Ruth only goes up .029.

Bonds falls .082 at age 37 but Ruth falls .132. At age 38 Bonds goes down .153 but Ruth goes down almost as much, .144. But you have to remember, Bonds is coming down from what are his two highest years and they are both much higher than any of his younger years. For Ruth, his best years were all when he was much younger.

At 39, Bonds actually goes up again, by .123 while Ruth falls again, this time by .146.

Ruth's Rel SLGs at ages 37-39 are all much lower than for any age from 31-35. But for Bonds it is the opposite. His Rel SLGs from age 37-39 are all much higher than for anything from 31-35. And again, his four highest Rel SLGs are all from ages 36-39 (and by a wide margin). This must be extremely rare.

This next table shows their Rel SLGs over two age periods: 24-35 and 36-39.

Player	24-35	Lg	Rel
Bonds	0.591	0.402	1.470
Ruth	0.733	0.397	1.846
Player	36-39	Lg	Rel
Bonds	0.809	0.419	1.931
Ruth	0.628	0.397	1.582

So Bonds had a Rel SLG of 1.470 from ages 24-35 (.591/.402). Then it jumps to 1.931 from ages 36-39. So his older period is 31.3% higher (1.931/1.470 = 1.313). But Ruth actually declined 14.3% (since 1.582/1.846 = .857 and 1-.857 = .143).

That is a swing of 45.6 percentage points. And notice that older Bonds (1.931) is better than younger Ruth (1.846). Ruth only had 4 seasons that match or exceed the 1.931 Bonds had over ages 36-39 and the oldest of them was at age 32. The others were at ages 25, 26 and 28.