Koshien Stadium is famous for being a terrible home run park, particular when the balls are hit to right and run into the wind blowing in off Osaka Bay. This got me curious enough to see how that effect compared to NPB’s other parks.
Of course, right-handed hitters hit home runs more frequently than left-handed hitters in EVERY NPB park, not because of the park’s dimensions or wind, but because slap hitters who rarely drive the ball make up a much larger percentage of NPB’s left-handed-hitting population.
To figure out which parks help which kinds of batters, I’ve gone to weighted averages of home run rates (AB divided by HR) with a minimum of 100 at-bats in each target park. Because a lower number indicates more home runs per at-bat, the best home run parks will have factors below 1, and the worst home run parks greater than 1. The figures for two parks that changed in 2019, Yokohama and Chiba’s Zozo Marine, are only counted from 2015 to 2018.
Central League
| Park | LHB | RHB |
| Koshien Stadium | 2.27 | 1.40 |
| Nagoya Dome | 1.51 | 1.75 |
| Tokyo Dome | 1.19 | 0.76 |
| Mazda Stadium | 1.15 | 1.32 |
| Yokohama Stadium | 0.86 | 1.11 |
| Jingu Stadium | 0.74 | 0.67 |
No surprise to see Jingu as the CL’s home run heaven, while Nagoya Dome and Koshien are by the toughest two to clear the fences. The surprise was that Tokyo Dome and Yokohama showed so much variance between LHB and RHB.
Pacific League
| Park | LHB | RHB |
| Kyocera Dome | 1.60 | 1.66 |
| Sapporo Dome | 1.32 | 1.23 |
| Rakuten Seimei Miyagi | 1.28 | 0.99 |
| Zozo Marine Stadium | 1.00 | 1.45 |
| MetLife Dome | 0.92 | 0.91 |
| Yafuoku Dome (now Pay Pay Dome) | 0.85 | 0.85 |
