Did Major League Baseball Actually Have a "Steroid Era"?

The Steroid Era in major-league baseball from 1994 to 2004 saw a dramatic increase in home runs and career resurgences of late-career players. Anabolic steroids and other performance-enhancing drugs (PEDs) were widely accepted as the explanation, but baseball quants never found that convincing. One reason is illustrated in the chart below.

The statistical signature of the Steroid Era was the ratio of home runs to singles. Players didn’t get more hits, but more of the hits left the park. The chart shows the home run/single ratio by season, color coded by baseball era. The ratio did increase rapidly in the Steroid Era, but not as dramatically as in the Live Ball and Integration Eras. Moreover, the big picture seems to be a steady increase since organized professional baseball began.

People invent after-the-fact explanations for the eras—based on rule or equipment changes, more teams, increased player diversity, new ballparks, etc.—but none of these survive skeptical challenges.

In 2004, superstar statistician Nate Silver wrote that it would take ten years to determine if steroids were the cause of the Steroid Era. The subsequent ten years (the first part of the brown Post-steroid Era line on the right of the chart) seemed to indict steroids. MLB implemented serious testing in 2005, and the home-run/single ratio dropped.

Case closed? It might have been except for the following ten years, 2015 to 2024. The home-run/single ratio soared far higher and faster than any time in the past. If steroids caused the Steroid Era increases, are new super-PEDs evading the drug tests? Or were players taking steroids merely scapegoats for the Steroid Era changes?

If there is a nefarious explanation for the current power surge in baseball, we should look for it. If steroids did not cause the Steroid Era, we should rethink our attitudes to players who used PEDs.

Steroids in baseball are not new. In 1889, pitcher Pud Galvin was a user and vocal proponent of testosterone supplements. The Washington Post wrote at the time, "If there still be doubting Thomases who concede no virtue to the elixir, they are respectfully referred to Galvin's record in the Boston-Pittsburgh game. It is the best proof yet furnished of the value of the discovery."

A century later, after the 1988 season, the Washington Post remained unconcerned. Sportswriter Thomas Boswell wrote that the American League Most Valuable Player José Canseco was, “the most conspicuous example of a player who has made himself great with steroids.”

Players used all sorts of other supplements, including amphetamines and pain killers, and no one bothered to hide it.

Cheating—and many of the alleged PED-users were not breaking either baseball rules or the law—has never been considered shameful in baseball. Pitchers doctored baseballs, hitters doctored bats, groundskeepers altered the field, coaches stole signs, infielders tripped or grabbed runners. Prior to 2005, the standard was if you got caught you took your fine or suspension, but no one thought less of you. Only gambling on baseball or throwing games was considered scandalous, and more recently sign-stealing has been added to the list.

The reason for the change of heart about PEDs was the idea that they had tainted the record books with spectacular accomplishments due to chemistry rather than player skill or work. But if PEDs were not responsible, then there’s no reason to taint Steroid Era statistics.

Exoneration of steroids does not depend solely on the home-run/single ratio. The most home runs any team had hit in a season up to 1995 was 240 by the 1961 New York Yankees. In 1996 three teams hit more home runs. Over the ten seasons from 1996 to 2005, eleven teams hit more home runs than any major-league baseball team had managed from 1872 to 1995.

In the next 12 years with PED-testing in place, only three teams hit more than 240 home runs, suggesting that PEDs were responsible for the Steroid Era surge. But in the last eight years (really only seven years as the 2020 season was COVID-shortened), 20 teams have smashed the record, including three with over 300 home runs.

Looking at aggregate statistics is a crude way to test for PED influence. Although public attention has focused on the top players alleged to have used PEDs, baseball quants look for a more specific signature—a player in his 30s who undergoes a sudden power surge to well above his performance in his 20s. Up to age 30, for example, outfielder Steve Finley hit 47 home runs and 701 singles, a ratio of 6.7%. From age 31 to 42, he hit 293 home runs and 1,075 singles, a ratio of 27.3%. The transformation occurred in 1996. This is what quants take more seriously than headlines like Barry Bonds hitting 73 home runs in 2001.

Finley’s transformation is a 36 standard deviation event, although we can’t take that literally. In 1995 ten MLB players had transformations that we would expect to happen to only one in 1,000 players by random chance, although in fact about one in 100 players (211 out of 20,596) have manifested 0.1% power surges. Nine players did this in 1992 and eight more in 1993 (1994 had only four, but the year was strike-shortened). Before anabolic steroids the most players in any year was six in 1920—the birth of the Live Ball Era.

The table shows the number of 0.1% transformations by era. The raw numbers can be misleading since the eras cover different numbers of seasons, with different numbers of major-league baseball teams. So I have adjusted all numbers to match the number of players from the Poststeroid Era.

This suggests that dramatic Steroid Era player transformations are not out of line with other eras, including the present.

None of this proves PEDs were unrelated to baseball statistics from 1993 to 2004, but it does undercut the conventional case based on team and individual home run totals, player power surges and other statistical evidence. There seems little reason to consider statistics compiled in the Steroid Era to be tainted, nor for players caught or suspected of using PEDs to be treated differently from cheaters in other eras.