Keeping Score

Bonds, Clemens, And The Hall Of Fame: A Physicist’s Take

Looking inside the analytics of baseball, steroids, and the Hall of Fame

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Jed Jacobsohn / Getty Images

Barry Bonds takes a swing against the San Diego Padres in 2004. In his first year on the Hall of Fame ballot, Bonds was not voted in

In sports, we’re so used to looking at totals, and judging a player’s worth based on these raw numbers. How many RBIs does he have? How many rebounds has he grabbed?

But if the sports analytics movement has taught us anything, it’s that more often than not, percentages tell a truer story. A player may compile lots of RBIs because he happens to have talented teammates that actually get on base. But shouldn’t his value be judged on the percentage of available runners he drives in? A basketball player may grab a ton of rebounds, but is that because he happens to play for a good defensive team, which produces more missed shots, and more available rebounds to grab? Shouldn’t we look at the rate of which he grabs available rebounds?

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Before the Baseball Hall of Fame announced that the baseball writers did not elect any players to the class of 2013 — the first time this has happened since 1996 — Dave Cameron, managing editor of, the insightful baseball analytics site, posted some numbers that reminded us of the power of percentages. Cameron, who said he would have voted for Barry Bonds and Roger Clemens — players with two of the greatest statistical careers of all time, but who were excluded from the Hall this year, their first on the ballot, because of their connection to performance-enhancing drug use — makes the argument that the impact of PEDs on baseball is overstated. The popular narrative, Cameron notes, is that since home run totals spiked during the late 1990s and early 2000s, and then declined when drug testing became more stringent, steroids were responsible for the inflated home run totals.

(MORE: Bonds, Clemens Rejected; No One Elected To Baseball Hall of Fame)

“To those who tell you that,” Cameron writes, “please ask them to explain this simple fact.”  Cameron then notes that when players make contact in today’s game, they’re hitting the ball out of the park at pretty much the same rate that they did during the steroid era. In 2012, 3.8% of all balls put in play went for home runs. In 1998, the year Mark McGwire hit 70 homes runs, and Sammy Sosa slugged 66, 3.7% of all contact plays sailed out of the park. From 1999 through 2001, the peak of the steroid era — Bonds hit a record 73 home runs in 2001 — home runs per balls in play were at 4.0%, 4.1%, and 4.0%, respectively. In other words, almost the same as it is today.

“The drastic decrease in home runs since the inception of PED testing is due mostly to the dramatic rise in strikeouts we’ve seen over the last five years,” writes Cameron. “The league average strikeout rate hung at around 17% for most of the “steroid era,” but climbed to a record high 20% last year.”

“If you put forth the current run environment as an example of what baseball looks like without PEDs, please understand that you are arguing that PEDs caused hitters to be able to make contact more often, not hit the ball over the wall more often when they did make contact. That is what the facts demonstrate. We’re all entitled to our own opinions, but we aren’t entitled to our own facts. And the fact is, the rate of home runs on contacted balls was higher in 2012 than it was in 1998.”

But Roger Tobin, a physics professor at Tufts University, argues the PEDs can cause more batted balls to go over the fence. “My research shows that based on the physics and physiology that we know,” Tobin says, “muscle mass from steroid use is sufficient to turn a player with the home run productivity of a Hank Aaron into a player with the home run activity of Barry Bonds. So in that sense, no, I don’t think the impact of PEDs is overstated.” In a study published in the American Journal of Physics in 2008, Tobin’s calculations show that thanks to a 10% increase in muscle mass from steroids, “the speed of the bat as it strikes the pitched ball will be roughly 5% higher than without the use of steroids.” And thus, the speed of the ball as it leaves the bat will increase by 4%. Accounting for gravity, air resistance and lift force from the ball’s spin, Tobin concludes that his jump “can increase home run production by anywhere from 50 percent to 100 percent.”

(PHOTOS: The Evolution of Barry Bonds)

But what about the pitchers? One reason Cameron thinks that the steroid impact on home runs is overstated is that they were also using performance-enhancers. As Tobin himself writes in his paper, “when the first results of drug testing in professional –mainly minor league–baseball were announced in 2005, 31 of the 68 suspended players—46%—were pitchers.” So shouldn’t this cancel out any advantage?

No, says Tobin: his mechanical analysis shows that although a 10% increase in muscle mass could add 4 to 5 m.p.h. to a pitcher’s velocity, “the unusual sensitivity of home run production to bat speed results in much more dramatic effects, and focuses attention disproportionately on the hitters.”

But what about Cameron’s numbers, showing that as a percentage of balls put in play, the home run rates today are similar to those in the steroid era? That may be true for all of baseball, Tobin says. The elite power hitters of the steroid era, however, were hitting more batted balls out the park than prior stars, because these were the players for which the extra muscle boost could dramatically impact their home run numbers. These players were already more likely to hit long fly balls without steroids: the juice would make a difference. So they had much more incentive to juice. And if weaker hitters were juicing, PEDs could give them more power, but maybe not as much to impact home run production.

Take Bonds, for example. In 2001, the year he hit 73 home runs, 19% of the balls Bonds put in play were home runs, Tobin shows. In his five best years putting balls in play into the stands, Bonds averaged a 15% home run per contact rate. Babe Ruth’s five best years averaged 9.2%. Aaron’s: 6.8%. Willie Mays‘: 5.2%. Mark McGwire’s: 17.2%.

Yeah, I’m betting that the performance-enhancers made a difference.

But even though Cameron and Tobin disagree about the impact of steroids, they both think players like Bonds and Clemens should be in the Hall of Fame. “These are the greatest players of their generation,” says Tobin. “You can never prove that anyone in that era was clean.” If anything, Tobin recommends a separate Hall of Fame wing for steroids-era stars. “If someone went to the Hall of Fame in 25 years, and all these guys are missing? That would just seem weird to me.”

MORE: Lesson of the Barry Bonds Steroid Trial? No More Steroid Trial!