The Yankees led all of baseball with 241 home runs last year, the 16th highest single-season total ever by a team. Aaron Judge set a MLB rookie record with 52, while Gary Sanchez’s 33 and Didi Gregorius’s 25 were franchise records for a catcher and shortstop. You knew all of that already. As Maude Lebowski said, “…and proud we are of all of them.”
For the first time in baseball history, the average MLB team hit more than 200 home runs; in fact, they averaged 203.5 home runs per team. The league average fluctuates greatly from year-to-year and even more so across eras. For comparison, here are the MLB team average HR for the last 6 seasons.
|Year||Avg Team HR|
Homers increased 69% from 2014 to 2017. Going further back, we can see even greater differences. The average team hit 93.1 HR in 1976, 151.7 in 1961, and 56.6 in 1943, to pick just a few examples. Looking at every MLB team’s HR total from 1920-2017, the overall average is 129. (Prior to 1920 hardly anyone hit more than a handful of homers, which is why it’s known as the Deadball Era.)
HR is a counting stat, so we normally just celebrate who blasted the most baseballs over the fence. We don’t often think about HR relative to league average. Doing so would show that the 2017 Yankees’ 241 HR is not that special when the league average is as high as 203.5.
Standard Deviations and Z-Scores
To measure HR relative to the league, we’ll need to calculate the standard deviation of the league average for each season. This tells us how spread out each team’s HR totals are from each other in a given season. Then, we can find the Z-score for each team, which is how many standard deviations their HR total is away from the mean.
For 2017, one standard deviation away from the mean of 203.5 was 22.7 HR. The Yankees led MLB with 241 HR, which gives them a Z-score of 1.65. This is actually one of the lowest Z-scores for a league-leading team in history! 2017 was the first season since 1989 in which the HR leading team had a Z-score lower than 2. In fact, the only team to ever lead the league in HR with a lower Z-score was the 1959 Milwaukee Braves.
The Yankees’ 241 HR in 2017 was equal to the 1925 Giants’ 114. Baseball was really weird back then.
The Best of Home Runs
Let’s try an experiment. If Giancarlo Stanton had played for the Yankees last year and added 59 home runs, the team total ascends to an even 300 HR (we’ll ignore the fact that other players would’ve lost playing time and hit fewer home runs with Stanton in the lineup). That would obliterate the MLB record of 264 home runs set by the 1997 Mariners. The 2017 Yankees + Stanton brings the Z-score to 3.63, which is much more impressive. But how would this hold up against the best home run hitting teams of all time? For that matter, how do the 1997 Mariners fare relative to the league?
Here are the top 10 Team HR Z-scores from 1920-2017:
Unsurprisingly, the 1920 Yankees have the highest Z-score ever. The league average that year was 39.4 HR, and Babe Ruth had 54 all by himself. The second place team was the Philadelphia Athletics with 64, and every other team hit less than the Babe.
More recently, the 2010 Blue Jays’ had the third best Z-score. This means that their 257 HR was more impressive than the 1997 Mariners’ record of 264. Ken Griffey Jr., Jay Buhner, and friends actually had the seventh best team HR season ever, and not the best.
The Worst of Home Runs
What about the other end of the spectrum? If we can use standard deviation and Z-score to find the best home run hitting teams we can also use them to find the worst. Here’s the bottom 10 by Z-score:
It looks like we really did see an almost-record last season, just not a good one. The 2017 Giants were the second worst team in history at hitting home runs. It’s important to point out that Z-score doesn’t account for park factors, and their home stadium repressed offense overall by 9%. Even still, they failed to produce a single 20 HR hitter during a season in which homers exploded around the league.
Let’s talk about those 1980s Cardinals. The league average was 146.7 HR in 1986, yet they only managed 58. This gave them a -3.70 Z-score, the worst ever. Three years later they produced the fifth worst HR Z-Score. Not pictured above is the 1987 Cardinals, who just missed the chart with the 11th worst HR Z-score.
The amazing thing about these Cardinals isn’t just the consistency with which they failed to hit dingers, it’s that they were still a good team! Led by the speed and defense of Ozzie Smith, Willie McGee, and Vince Coleman, the 1987 Cardinals finished 95-67 and took the Twins to the seventh game of the World Series! Other than the 1987 and 1989 Cardinals, the only team to finish over .500 with a bottom 10 HR Z-score was the 1979 Astros (the 1986 Cardinals were 79-83).
This Kinda Sucks
This is not fun. It’s much more enjoyable to revel in the brutish destruction of baseballs perpetuated by Judge and company. We’re not better off knowing that the 2017 Yankees were one of the least impressive league-leading HR teams in history. This whole experiment has been a buzzkill. Here’s something to cheer us all up:
All statistics other than standard deviations and Z-scores courtesy of Baseball-Reference.
Photo Credit: Adam Hunger-USA TODAY Sports