Introduction
In my recent Comparing Home Run Rates for Two Seasons post, I wondered about home run hitting in the coming season. On one hand, I predicted that batters would continue to hit with “home run friendly” launch conditions, that is higher launch speeds with launch angles between 20 and 40 degrees. But the characteristics, specifically the drag coefficient, of the 2022 balls are unknown. I know that MLB admitted to using deader balls in the 2021 season and indicated in a team memo there would be no change to the 2022 ball. But we won’t know for sure about the properties of the 2022 balls until we see some data.
Eleven Days of Baseball
We have Statcast data that provides the launch angles, exit velocities and outcomes (home run or not) for all batted balls in the 2022 season through yesterday’s games (April 17). I know this isn’t much data (eleven days of games) and home run rates tend to be a little depressed during the cold month of April. But there are clear patterns in batted ball and home run rates in this data. I predict that the total home run count in the entire season will be significantly smaller than the 2021 home run count of 5944.
Historical Look at In-Play Home Run Rates
Let’s start with a historical view of the rate of home runs per balls put into play, defined by
HR Rate = HR / (AB – SO)
The following graph shows the HR Rate for the seasons 1980 through 2022 (I’m using data from Baseball Reference.). Note the big drop in HR rate from about 5 to 4 percent from 2021 to 2022. In fact, the current in-play HR rate is similar to the rate for the steroids seasons around 2000. Sure, there is a small weather bias but that is not enough to account for the one percent decrease (from 5 to 4 percent) in HR rate.
Batted Ball Rates
To hit a home run, one needs to hit the ball hard with a good launch angle. Let’s focus on the batted balls where the launch angle is between 20 and 40 degrees and the exit velocity is between 95 and 110 mph. The following plot shows the fraction of these “home run friendly” batted balls for the period April 1 through April 17 over the Statcast seasons. Note that there is a steady increase in this rate and the 2022 rate is a little higher than 2021. So the players are hitting the ball as hard in 2022 as they were in the 2021 season.
Home Run Rates
What is the chance that these “home run friendly” batted balls are home runs? We focus on the balls where the launch angle is between 20 and 40 degrees and the exit velocity is between 95 and 110 mph. Here I have graphed the home run rate of these batted balls over the Statcast seasons over the same April time period. Note the sharp decrease in this home run rate from 2021 to 2022.
The 2022 Ball
The reason why the current in-play home run rate is so low is that the 2022 balls appear to be relatively dead. In other words, the drag coefficient of the 2022 ball appears to be significantly higher than in the previous seasons. The balls aren’t carrying as far and this will have a significant impact on home run hitting and MLB offenses this season.
I will continue to monitor these rate measures as the season progresses.
Exploring Baseball Data with R 