With home runs up, what ballparks have had an effect?

In 2014, Major League Baseball saw the fewest home runs hit since 1995. Now, a scant two years later, 2016 has seen the 7th most home runs hit in a season, ever, and there still about 500 games to play. The league in general has seen a large rise in HR/FB rate, from 9.5 percent in 2014 to 11.4 in 2015 and up to 13 this year, which is easily the highest HR/FB rates since 2002.

Much ink has been spent talking about juiced balls and possible changes in batting approach, but I wanted to have a look to see if any specific ballparks are having an effect on the home run production. I did this by looking at the average number of home runs from each ballpark from 2011 to 2015, and then looking to see which ballparks were up the most this year over that five year average.  Let’s have a look at the top five largest discrepancies.

Safeco has seen the largest increase this year over the five year average from 148 to 209 this year. The average ballpark has seen a 15.2 percent home run increase, so that is quite the jump. This isn’t all that unexpected, as Seattle moved the fences in before 2013 and saw a large increase in 2013 and 2015, but having the third most home runs this year is notable, even if they did move the fences in.  

There may be something to the way Safeco is playing this year, as the Seattle Mariners are giving up 1.4 HR/9 at home but only 1.2 while on the road, while the batters are hitting 17.1 percent in HR/FB at home and only 14.8 on the road.

Target Field has the second-largest increase at 48.4. This one might be pitching staff related, as the Minnesota Twins have seen their HR/FB number shoot up from previous years. The entire league has seen its HR/FB rate for from 9.5 percent to 11.4 to 13 over the last three years, but the Twins have been especially affected this year going from 8.3 percent in 2014 to 10.4 last year to 14.2 this year.  

This also doesn’t seem to be a ballpark specific malady for the Twins, as they are giving up 13.8 percent HR/FB on the road and 14.3 HR/FB at home. This is further backed up by Twins hitters hitting 12.8 percent HR/FB at home and 13.8 on the road.

Chase Field comes in at number three on our list with 46.8 more home runs than its previous five year average. Park factors at ESPN show that Chase Field has been a home run friendly park in 2011, 2012, and 2014, but not to the degree it is playing this year.  There also appears to be something going on at Chase Field as Arizona Diamondback pitchers are giving up 1.38 home runs at home while only giving up 1.19 homers on the road.  The hitters are seeing an even bigger split with 17.5 percent HR/FB at home and only 11.4 on the road.

Busch Stadium is up next, and I was quite surprised to see this jump of 40.2 home runs over the previous 5 year average. I was even more surprised, after the St. Louis Cardinals recent bout of hitting a homer every time they took the field, that their HR/FB at home is only 14th in the league, but the jump from 8.5 percent last year to 13.2 this year, especially with Cardinals hitter having a 16 percent HR/FB rate on the road, probably explains most of that jump. The park may be contributing some to the pitchers as well, as the pitching staff is giving up 13.4 percent HR/FB at home and 12.4 on the road.

The last stadium we will look at is Comerica Park. The Detroit Tigers’ home park saw an increase of 36 home runs over its 5 year average. The Tigers are seeing a large difference in their pitching home and away as they are tied for the least HR/9 in the league at 0.9 while their home HR/9 is 1.3, or ninth highest in the league. Their hitters are not having a similar experience, as they are hitting 13 percent HR/FB at home and 13.9 HR/FB on the road.

The thing that struck me the most in this exercise is was that the most home run friendly parks were not leading the charge in giving up more home runs. In fact, Camden Yards, Rogers Center, Coors Field, and Miller Park have all seen fewer home runs than they have in the previous five year sample (Miller Park, Coors Field, and Rogers Center may still catch the previous average before the end of the year).  

Because of this, I decided to look into what percentage of total home runs in all of Major League Baseball came from each ballpark (total ballpark home runs/total MLB home runs) and to see how that has been affected this year. If all other things were equal, each ballpark would have a 3.33 percent share of the home runs.

I used the same five-year average, and then compared to this year. Camden Yards has gone from 4.59 percent of the league-wide home runs to 3.82 this year. The Rogers Center went from 4.33 percent of the league-wide home runs down to 3.79 this year. In fact, eight of the nine highest home run shares over the sample were down this year.

Overall, it seems like a mixed bag over the highest home run rises between on-field performance and some stadium changes. It also seems like the home run charge is not being led by the ballparks most would expect.