HR Rates and Steroid Use

I know, I know – I put up a ‘Final Word’ post on McGwire fully intending that to be the last thing I ever said on the subject.  While browsing through the BBA website, however, I happened on this article by Nick Scala which talked in passing about McGwire’s HR rates over the course of his career.   Basically it poked a huge hole in McGwire’s assertion steroids didn’t help him hit home runs, because his HR rate (defined as how many at bats between home runs) got better as he got older.  I started thinking, how does McGwire’s HR rate compare to the average AB/HR rate?

Compiling HR rate data for the tens of thousands of men who’ve played major league baseball proved too daunting a task in a short time frame.  Perhaps at some point in the future I’ll do that.  For this analysis, I decided to limit my data to the men who hit at least 400 home runs over the course of their careers.  I surmised that since these 45 guys were the most successful home run hitters in the history of baseball, their average AB/HR rates would be representative of the best rates possible in MLB.  Since all these men have played in differerent eras, I decided to calculate the rates based on age; that way, a comparison between Ruth at 25 can be made with McGwire at 25, and so on.

394,694 at bats, and 23,320 home runs make up this data set.  Here’s what the AB/HR Average graph looks like for the 400+ HR club:

A comment on this graph for completeness.  Four members of this club appeared in games at the Major League level before turning 19 (Jimmy Foxx and Mel Ott at 17 and 18, A-Rod and Killebrew at age 18), and in 331 at bats between them they hit 1 home run.  That makes a rate of ‘can’t divide by 0’ for the 17-year olds, and ‘262’ for the 18-year olds, so I omitted it from this graph.

That said, you can clearly see the trend.  AB/HR rates drop until players reach their mid-20s, then plateau until about age 30 and gradually get worse until they retire.  Only Yaz and Winfield were still playing at 43, by the way (495 AB, 12 HR).

A couple of representative graphs.  Here’s Ruth:

Here’s Frank Robinson:

Here’s A-Rod:

Here’s Musial.

The HR rate arc for these players match the Average trend.  Now, here’s three more:



And Darrell Evans:

Of the 45 players I looked at, these are the only three who showed sustained improvement in hitting HR at the end of their careers, where sustained is three or more consecutive seasons with a AB/HR rate lower than their previous average.  I am NOT accusing Darrell Evans of using steroids, because  I believe Darrell Evans’ success can be mostly explained by his move from Candlestick Park to Tiger Stadium.  That said I did not expect to find another hitter with showing improvement in their ability to hit HR’s out after their 35th birthday.

McGwire’s and Bonds’ rates not only lower as they get older, but their rate graphs also have remarkably similar slopes.  Unless they each unlocked a secret of hitting unknown for the first 130 years of professional baseball in this country – not unlikely, but certainly a little far fetched – there’s something else going on.

McGwire can claim, and believe, his steroid use did not improve his ability to hit home runs.  The data does not support that conclusion.

Update 23 Mar 10:  At long last, I have Acrobat files for the data.  I’ve broken them into three parts:  HR v Steroid Use – Summary Sheets, HR v Steroid Use – Graphs, HR v Steroid Use – Raw Data.  Enjoy.



Filed under Baseball Bloggers Alliance, General Baseball, SABR

5 responses to “HR Rates and Steroid Use

  1. That’s some very heavy lifting. Nicely done.

  2. Excellent work. Very informative. Thanks for taking the time to do this. Can’t wait till the full list is posted. Would like to be able to reference “clean guys” like Frank Thomas.

  3. Dang Mike, some heavy lifting indeed.

    Very thorough analysis of these numbers.

    You reference Evans’ move to Tiger Stadium – I’m curious what affect, if any, new parks had on Bonds and McGwire?

    Going from Candlestick to a RF porch set up for him in whatever San Fran’s park was called in those days surely was a boon for Bonds – likewise McGwire from expansive Oakland Coliseum to Busch II.

    Obviously not enough impact to skew the numbers as they’re shown, but I’m still curious nonetheless.

  4. Mike

    Nick that’s a great question on park effect. I’ll take a look at that and post a follow-up.

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