Five years ago, Yankee Stadium opened up to much controversy from diehard Yankee fans and rival fans alike. Most Yankee fans were unsure about losing the historical significance of the original Yankee Stadium, or whatever was left of it after the mid-70's renovations. After the first month of baseball in the Bronx, a majority of the Yankee fans embraced the new stadium as it demonstrated its early quirks. At the end of April 2009, Buster Olney started controversy by questioning the stadium's airflow. The article, entitled New Yankee Stadium on steroids? pushed forward a theory that the alignment of the new stadium created wind tunnel conditions that allowed typical outs to become home runs and extra base hits. This started a narrative by a countless number of broadcasts that lasted through the month of June, home runs in Yankee Stadium weren't really home runs.
"With the way the wind has been the last couple of days, right field is a joke," one official said. "I would say at least three or four home runs in this series would be routine outs in nearly every park."
Now that we have half a decade worth of data, we know the real reason for the incredible home run rate in the ballpark's initial season. The 2009 Yankees were really really good. Statistically, the 2009 Yankees put together an average 117 wRC+, which makes them the second best offensive team over the last ten years to the 2007 Yankees. (119 wRC+) Their pitching wasn't too shabby either, however, the first month of the season showcased poor performances by Chien-Ming Wang and A.J. Burnett, which didn't help bring down the home run rates.
There's no denying that Yankee Stadium's short porch plays into the left-handed power of their lineup. Since the stadium opened, the Yankees have hit 601 home runs in the Bronx, while hitting just 476 on the road. But the idea that so many home runs in Yankee Stadium are outs in most parks has also been disproven. Despite the surplus of home runs at home, the Yankees still maintain a tremendous number of extra base hits on the road, and when counted equally, the team has been remarkably consistent. As opposed to their home-away home run differential, the Yankees have just 680 doubles and 45 triples in their home ballpark, which is far less than the 766 doubles and 82 triples on the road. Over the last five years, that's 1,326 extra base hits at home and 1,324 extra base hits on the road.
The wind tunnel conditions in Yankee stadium were likened to the altitude issues in Coors Field. Though we're not dealing with wind, the Rockies undoubtedly benefit from their home ballpark by gaining a ton of extra base hits that should be outs or singles. Looking over the same time span, the Rockies have hit 1,501 extra base hits at home, while on the road they've hit just 1,114. Where the Yankees had just two more extra base hits at their home ballpark over the last five seasons, the Rockies have 387.
After a month of the wind tunnel narrative in countless broadcasts in 2009, Jayson Stark grew a little more scientific on the subject by studying a hit tracker. When comparing to different ballparks, Stark found that just two of the first seventy home runs hit in Yankee Stadium wouldn't be home runs in one of the 29 other ballparks.
But then the home runs slowed down. Old Yankee Stadium was eventually torn down, and apparently the wind currents from the river hit Yankee Stadium differently thereafter. Most of the believers in the wind tunnel theory used that to justify why the home runs stalled.
And then the home runs started again. The Yankee actually hit more home runs in 2012 (245) than they did in 2009. (244) Meanwhile, Greg Rybarczyk of hittrackeronline.com showed that the new Yankee Stadium actually had different dimensions than the old ballpark. For the most part, the theory about new Yankee Stadium is the same as the old one, that the short porch simply helps their lefty-heavy lineup turn doubles and triples in to home runs.
In the end, the dimensions of Yankee Stadium certainly help batters hit home runs, but the idea that a wind current inside Yankee Stadium turned normal outs into home runs is largely debunked. Over the last five years, the Yankees have just 2 more extra base hits at home than they have on the road, an incredibly insignificant difference. Today we can recognize that the wind tunnel theory towards the early home run flood in new Yankee Stadium was just an excuse for those unwilling to recognize that the Bronx Bombers were simply that good in 2009.