# Everyone is Hitting Home Runs

#### Introduction

Home runs are certainly in the news this All-Star Baseball week. Justin Verlander claimed that the baseball is juiced and the MLB Commissioner Rob Manfred has emphatically responded that the MLB has not altered the baseball to produce more offense.

One fascinating aspect of the 2019 home run hitting is that many players are hitting a lot of home runs. It seems that any MLB non-pitcher, given a fastball or offspeed pitch located in the middle of the zone, can hit the pitch for a home run.

I was thinking of some way of quantifying the idea that the total home run count is spread among many players. Let’s go back in time to the 1920 season — I have listed the ten home run leaders. In addition, I compute the cumulative count of home runs and the percentage of the home run total achieved by these top players. Babe Ruth, with his 54 home runs, hit about 9% of the total home run count for that season. The top 10 hitters hit collectively 28% of the home run count. In 1920, there was a clearly defined group of “sluggers” who accounted for a large percentage of home runs.

#### Compare Four Home Run Seasons

Let’s use this idea to compare four seasons noted for home runs.

• 1920 was one of those seasons where Babe Ruth was the dominant home run hitter.
• 1961 had the great Roger Maris/Mickey Mantle home run dual where Maris hit 61* home runs (we all know why an asterisk was added, and later removed from this number in the record books)
• 1998 had the great Mark McGwire/Sammy Sosa home run dual — McGwire hit 70 home runs this season
• 2019 will very likely set a record for the total number of home runs hit

For each season, I found the leaders for home runs. For the top k home run hitters each season I computed the percentage of home runs hit by these k leaders. I plot the number of players (horizontal) against the percentage of home runs hit (vertical) by this number of players for each season.

There are clear differences between these seasons. For example, how many players hit 30% of the total home run count? The answers (reading from the graph) are

• 12 players in 1920
• 24 players in 1961
• 38 players in 1998
• 51 players in 2019

#### Is this a Fair Comparison?

This comparison is a little unfair since the number of teams has changed over the history of baseball. So let’s focus on the seasons 1998 through 2019 when we had 30 teams and roughly the same number of players. Below I graph the number of players for each season who hit 50% of the total home run count. The number of players rose from 85 to about 92 between 2005-2010, and has steadily increased from 2010 through 2019. Interestingly, the number of players hitting 50% of the home runs has dropped from 2018 to 2019 (first half).

#### Who Cares?

• In baseball history, when one thinks of home run hitting, one focuses on the home run leaders such as Babe Ruth, Roger Maris, Mark McGwire, and Barry Bonds. But things are different in 2019. The focus is not on the leaders, but rather the collective home run hitting among many players. I think my measure is helpful for getting a handle on the large number of players that are contributing to the total home run count. By this measure, 1920 is very different from 2019.
• I think this characteristic of home run hitting is changing how the game is played. Remember the 2004 season? Pitchers were afraid to pitch to the slugger Barry Bonds and he received a record number of walks (232) that season. Things are different now, since there is not a clear distinction between slugger and non-slugger and there is less motivation to pitch around batters, at least from a home run perspective.
• If MLB wants to change the total home run count, they need to do something that would impact the home run count for many players. Really, the bar for hitting a home run seems currently too low and some thing needs to be done to raise the bar.

### 3 responses

1. I think the “launch angle” theory was a ruse concocted by MLB as they interviewed Cody Bellinger and Christian Yelich last night and they both said that they didn’t use the theory or even know what it was.

2. “we all know why an asterisk was added, and later removed from this number in the record books”
Apparently, the Maris asterisk is an urban legend.
https://www.salon.com/2001/10/03/asterisk/