Barry Bonds's 73 home runs in the 2001 season are the most hit in any single season. Baltimore Orioles first baseman Chris Davis has 37 home runs heading into the All-Star break, prompting discussion of his chances of breaking the all-time record.
For some, though—including Davis himself—the Orioles slugger is being measured not against Bonds's 73 home runs, but rather the 61 hit by Roger Maris in 1961. Bonds's total, along with that of 61+ sluggers Mark McGwire and Sammy Sosa, is being disregarded amid hand-wringing over the sport's problems with performance-enhancing drugs.
But proponents of the Maris argument actually hurt the integrity of the sport by giving the role of PEDs in baseball far more credit than it deserves or has ever been given before. Davis' 37 home runs have him on pace to hit more than Maris, but fewer than Bonds—the first time this has happened since Bonds broke the record, and the first time the Maris vs. Bonds debate actually matters.
To be sure, MLB has a high-profile history of doping—enough that President George W. Bush explicitly called it out in his 2004 State of the Union address. Almost a decade later, the sport still has its share of PED problems; it is reportedly set to suspend several players after the All-Star break for their alleged involvement with a Miami clinic providing drugs. Stranger still, the suspensions circumvent MLB's own rules governing PED testing and punishment. That said, there are positive tests each year that demonstrate that doping still exists in baseball, though to a lesser extent than when PED use was at its peak in the 1990s and early 2000s.
What there is not proof of is of PED usage turning players into home-run hitters. When Congress released the Mitchell Report—the result of its nearly two-year investigation into doping in baseball—the list of players involved with PEDs was hardly a Murderers' Row of famous sluggers. For every Barry Bonds (762 career home runs) or Jason Giambi (435) listed, there were several players like Nook Logan (2) and Gary Bennett (22).
Additionally, it's important to note that even in the era of widespread doping, it wasn't just the users who started earning more home runs—league-wide, everybody started hitting more home runs. MLB has experienced a significant jump in the average number of home runs per game in the last few decades. As the graph below demonstrates, there was an enormous leap—nearly doubling the average from approximately one to approximately two in the early 1990s. Mark McGwire's 70 home runs in 1998 were hit in a season averaging 2.08 home runs/game. Bonds hit his 73 in a year where the average was 2.25. And as PED use has decreased among MLB players, the average number of home runs per game has maintained its high level: To date, Davis is hitting his home runs in a league with 1.99 home runs per game. If the increase in the early 1990s were solely attributable to PEDs, that number would have cratered back to its original in recent years—after more stringent testing was integrated into baseball. Instead, the power production in 2013 is far more similar to 2001 than it is to 1991. Clearly, there are variables in play beyond merely doping.
There is very little variation in the graph above after the 1994 jump. Between Bonds and Davis, there is a quarter of a home run per game's difference, which is far from the leap between the early and mid-'90s.
Quite simply, if one looks only at home runs per game, the league does not look that different between 2001 and 2013. Individual performances look similar to their 2001 levels, too: In 2001, 12 players hit more than 40 home runs, and in 2013, nine players are on pace to meet or surpass the 40-home-run mark. Both in the aggregate as well as at the individual level, there is little evidence that home runs are appreciably less frequent in 2013 than they were when McGwire or Bonds broke the record, even as PED usage has apparently decreased.