brewerfan.net header
About Us    Power 50    Link Report    Daily Brew    Draft    FAQ    Links
Transactions    Player Index    Login    Fan Forum
Lambeau Leap 1250 WSSP  
 
Brewerfan Features
Toby's Power 50
Link Report
Draft
Milwaukee Brewers
Nashville Sounds
Huntsville Stars
Brevard County Manatees
Wisconsin Timber Rattlers
Helena Brewers
Arizona Brewers



  Minor League
Player Search
 
 
 
Powered by
Baseball America

  Major League
Player Search
 
 
 
Powered by ESPN

  Poll
Should Tommy John be in the Hall of Fame?
1. Yes
2. No











 
Feature
 
 
Barry Bonds, Steroids and Home Run Power

Luzinski
on 03/12/2006

 

Barry Bonds has always been a great hitter. He has shown great plate discipline throughout his career, as is evidenced by his career .442 OBP. He has also always had exceptional power, with a career ISO of .381 as proof of that. What he didn't always have is "home run power", however. Despite putting up some gaudy slugging percentages in his 20's and early 30's, the highest home run total Bonds had ever achieved up to that point, was 46 in 1993, at age 29. While that was good enough to lead the league that season, a home run total in the 40's became nothing special as the 90's rolled on. League home run totals were ever increasing; Bonds' home run totals weren't.

It's not that uncommon for aging hitters to sustain their plate discipline. A Keith Woolner study showed an average year-to-year OBP decline after age 33 of only about 1.5%. The study also showed, however, that over the same period, the average player's home run/hit ratio decreased about four times faster. It made sense, then, when Bonds's home run power began slipping in his mid 30's. All of a sudden, Bonds's home run power not only returned, it was better than ever. He was 37 years old and breaking records. What happened?

McGwire's popularity as a result of breaking the single season HR record reportedly prompted Bonds, then 34, to begin taking performance-enhancing drugs after the 1998 season. Knowing the precise moment Bonds allegedly began using steroids allows for a more focused analysis on the possible effects these drugs may have had on his statistics. To measure Bonds's home run power, I'll use two metrics:

  • Percentage of balls-in-play that resulted in a home run (HR/(AB-SO))
  • Percentage of hits that were home runs (HR/Hits)

Let's track these two metrics throughout Bonds's career, making special note of any changes that occurred after his 1998 season (the year he allegedly began using steroids). The table below includes stats from Barry Bonds's entire career, with the exception of his injury shortened 2005 season:

Barry Bonds's Career "HR Power"

YR AGE AB H HR SO HR/BIP HR/H
1986 22 413 92 16 102 5.1% 17.4%
1987 23 551 144 25 88 5.4% 17.4%
1988 24 538 152 24 82 5.3% 15.8%
1989 25 580 144 19 93 3.9% 13.2%
1990 26 519 156 33 83 7.6% 21.2%
1991 27 510 149 25 73 5.7% 16.8%
1992 28 473 147 34 69 8.4% 23.1%
1993 29 539 181 46 79 10.0% 25.4%
1994 30 391 122 37 43 10.6% 30.3%
1995 31 506 149 33 83 7.8% 22.1%
1996 32 517 159 42 76 9.5% 26.4%
1997 33 532 155 40 87 9.0% 25.8%
1998 34 552 167 37 92 8.0% 22.2%
1999 35 355 93 34 62 11.6% 36.6%
2000 36 480 147 49 77 12.2% 33.3%
2001 37 476 156 73 93 19.1% 46.8%
2002 38 403 149 46 47 12.9% 30.9%
2003 39 390 133 45 58 13.6% 33.8%
2004 40 373 135 45 41 13.6% 33.3%

We can see that Bonds's home run power appeared to be diminishing in the 4 years prior to his 1999 season. The 1999 season erased that trend, and then some, however. The jump in both HR/BIP and HR/Hit after the 1998 season is dramatic. Let's look at the average of the 6 seasons before the 1998-1999 off-season and the 6 years after:

Barry Bonds, 1998-1999 Off-Season Split

  HR/BIP HR/H
Ages 29-34: 9.2% 25.4%
Ages 35-40: 13.8% 35.8%

Most players in their mid to late 30's would be hard pressed to even maintain the HR power they possessed in their late 20's and early 30's. Bonds somehow substantially increased his. How atypical is that, though?

I won't attempt to quantify the likelihood of Bonds's substantial increase in power so late in his career. It's a difficult, if not impossible question to answer. What I will do is simply compare Bonds's home run power to two other Hall of Fame sluggers, Babe Ruth and Hank Aaron. In doing so, we may be able to get a feel for how unusual Bonds's power surge has been.

I'll compare Bonds, Ruth and Aaron's home run power numbers for all seasons where they compiled at least 300 ABs. Fortunately, all three players had a run of at least 17 consecutive years with 300 or more ABs, making this comparison a pretty easy. First, the percentage of balls-in-play that resulted in a home run:

Second, the percentage of hits that were home runs:

Neither Ruth nor Aaron showed a systematic decrease in home run power in their mid to late 30's. In fact, it's clear that a late career home run power bulge like Bonds's is not without precedent. Excluding Bonds's freakish age 37 power numbers (almost 50% of his hits were home runs!), Aaron's numbers look very similar to Bonds's. Both showed a marked increase in home run power in their mid 30's. Clay Davenport of Baseball Prospectus has showed that there are many examples of hitters having their best home run season late in their career (Willie Stargell, Darrel Evans, Carlton Fisk and Harold Baines, to name a few). Of course, none hit 73 home runs, but an increase in home run power late in a player's career is not that uncommon.

There are many other factors which might justify Bonds's power increase, and Dan Fox points out a few of these in his career trajectory study. There has been evidence that elite batters tend to decline slower than the average batter. Furthermore, home run totals are higher as whole over the last decade. This could be a result of the prevalent use of steroids in baseball, or it could be a natural change in the balance between pitcher and batter. It could also simply be that Bonds's desire to hit more home runs later in his career caused him to increase the intensity of his strength training and change his approach at the plate. There are many factors, beyond steroids, that could have attributed to Bonds's home runs increasing after 1998.

This is, by no means, a comprehensive study. Without further study, it would be difficult for me to conclude that Bonds could not have compiled his late-career statistics without performance-enhancing drugs. While his pre/post 1998 stat differences are eye opening, they could still be reasonably justified without steroids playing a role. While the facts surrounding the allegations against Bonds indicate a high probability that he used performance enhancing drugs, the above statistics can't be used as conclusive proof.

Of course, nothing stops us from using common sense.

Appendix:

For those who are interested, I'll include the raw numbers that were used to make the above comparisons, again excluding the seasons with less than 300 ABs:

  Bonds Ruth Aaron
AGE HR/BIP HR/H HR/BIP HR/H HR/BIP HR/H
20 --- --- --- --- 3.0% 9.9%
21 --- --- --- --- 5.0% 14.3%
22 5.1% 17.4% --- --- 4.7% 13.0%
23 5.4% 17.4% 4.2% 11.6% 7.9% 22.2%
24 5.3% 15.8% 7.8% 20.9% 5.4% 15.3%
25 3.9% 13.2% 14.3% 31.4% 6.8% 17.5%
26 7.6% 21.2% 12.9% 28.9% 7.6% 23.3%
27 5.7% 16.8% 10.7% 27.3% 6.3% 17.3%
28 8.4% 23.1% 9.6% 20.0% 8.7% 23.6%
29 10.0% 25.4% 10.3% 23.0% 8.2% 21.9%
30 10.6% 30.3% 8.6% 24.0% 4.6% 12.8%
31 7.8% 22.1% 11.2% 25.5% 6.5% 17.7%
32 9.5% 26.4% 13.3% 31.3% 8.7% 26.2%
33 9.0% 25.8% 12.0% 31.2% 7.8% 21.2%
34 8.0% 22.2% 10.5% 26.7% 5.3% 16.7%
35 11.6% 36.6% 10.7% 26.3% 8.8% 26.8%
36 12.2% 33.3% 9.5% 23.1% 8.4% 24.7%
37 19.1% 46.8% 10.4% 26.3% 10.8% 29.0%
38 12.9% 30.9% 9.2% 24.6% 8.6% 28.6%
39 13.6% 33.8% 7.3% 21.0% 11.7% 33.9%
40 13.6% 33.3% --- --- 6.4% 22.0%
41 --- --- --- --- 2.9% 11.0%

References:

 




Email This Page   Printable Version  Return to Top   Return Home  
otherArticles
 
  Are Baseball Teams Streaky Over the Course of a Season?
(2007-08-27)
Barry Bonds, Steroids and Home Run Power
(2006-03-12)
Ben Sheets, Beyond the W-L
(2005-09-23)
If Only They Could Hit in The Clutch?
(2005-07-16)

Questions? Comments? Contact Brian Kapellusch (president, systems engineer) @
Brewerfan.net is a fan-based independent site, and is NOT affiliated with the Milwaukee Brewers Baseball Club.
Please support the Milwaukee Brewers by visiting their site at http://brewers.mlb.com