Because I live in Los Angeles, California, I spend a lot of time during the baseball season at Dodger Stadium. An interesting thing happens at Dodger Stadium that doesn’t happen at any other Major League ballpark. Well, a lot of things happen at Dodger Stadium that don’t happen at any other Major League ballpark. For instance, attempted homicide in the parking lot.

But what I’m referring to in this entry is that every time a fly ball is hit in Dodger Stadium, everyone stands up and cranes their neck to watch the ball’s flight. Well, not everyone. 40% of the Dodger Stadium crowd is, at any given point during a game, fixated on one of three hundred beach balls being batted around the stadium (they are not all fixated on this because they enjoy it; it’s also a legitimate safety concern for fans of visiting teams. I’ve been the victim of attempted beach ball assault on more than one occasion). But of the remaining 60%, a very large number stand up to watch every fly ball.

Every fly ball. It could be a pop-up to the catcher behind the plate. People will stand up. It could be a long, graceful foul ball that lands somewhere near Vin Scully. People will stand up. It could be a high, looping fly-out to the shortstop. People will stand up. People will stand up because in a city like Los Angeles, at any given time, there are fifty-seven things more interesting than watching the Dodgers. But even in a city like Los Angeles, home runs are one thing people understand and want to see.

What makes this behavior particularly odd is that fly balls don’t generally turn into home runs at Dodger Stadium. In 2012, 1.56 home runs per game were hit in Dodger Stadium. That’s the sixth-least of any stadium in Major League Baseball. In fact, every year since 2006 – when the ESPN Home Run Tracker was created – Dodger Stadium has been ranked as one of the top ten home run-suppressing stadiums in baseball.

Minute Maid Park, of course, has the opposite reputation. It’s known as a hitter-friendly park. One that encourages home runs. At least, that’s the reputation.

But in looking at the Home Run Tracker, something interesting pops up. Though it’s true that from 2006 – 2008, Minute Maid Park ranked among the top ten parks in home run rate, since then it has normalized, and in fact it’s currently listed as a fairly neutral park. In fact, the hitter’s advantage that MMP has been known for since its inaugural season of 2000 may not be such an advantage, after all.

Minute Maid Park Park Factors By Year (Batting)

Season	Park Factor
2000	107
2001	106
2002	106
2003	103
2004	101
2005	101
2006	100
2007	100
2008	97
2009	98
2010	97
2011	98
2012	99

After four seasons, Minute Maid Park stabilized and has been more or less a neutral park ever since. But whatever the offensive environment in Minute Maid Park, it’s been more or less understood that it allows more home runs – and fewer beach balls – than Dodger Stadium. Since 2006, an average of .43 fewer home runs a game per season. Over 81 home games, that’s almost 35 fewer home runs per season.

Which makes it even more puzzling what happened in 2010. In 2010, Minute Maid Park allowed just 1.59 home runs per game. Dodger Stadium allowed 1.62. One’s first instinct is to write this off as a bad offensive team, which isn’t entirely untrue, but remember that this covers visiting teams, as well. And as you can see, visiting teams didn’t exactly knock the ball out of Minute Maid Park, either (I include the Astros’ road splits for context):

Year	Home SLG	Road SLG	Visitors SLG
2008	.443	.389	.437
2009	.418	.383	.424
2010	.375	.349	.380
2011	.384	.364	.440
2012	.385	.358	.396

Astros’ hitters lost 43 points of SLG from 2009-2010 at Minute Maid Park, compared to 34 on the road. But visiting hitters lost 44 points themselves, only to completely rebound the following season.

A look at GB/FB rates doesn’t provide any answers:

Year	GB/FB	Home GB/FB	Visitors GB/FB
2008	1.31	1.42	1.16
2009	1.40	1.31	1.33
2010	1.36	1.34	1.22
2011	1.35	1.31	1.11
2012	1.36	1.42	1.53

Looking at home runs per fly ball yields some interesting results, however.

Year	HR/FB	Home HR/FB	Visitors HR/FB
2008	10.9%	12.4%	12.3%
2009	9.4%	6.1%	11.1%
2010	7.0%	8.2%	8.4%
2011	6.4%	6.1%	12.7%
2012	10.8%	12.4%	11.1%

The Astros’ HR/FB rates tumbled in 2010 – down 2.4% from 2009 overall, but actually up almost 2% at home. Conversely, however, visitors in Minute Maid Park only saw 8.4% of their fly balls leave the yard – a 2.7% reduction.

So what happened in 2010 that kept fly balls from leaving the stadium, for both the visitors and for the home team? I don’t see any evidence of a physical change that the stadium encountered that would have resulted in this.

One possible theory I can come up with is that Prince Fielder – who crushed the ball in Minute Maid Park – had a down year in 2010. Fielder slugged just .200 in Minute Maid Park in that season, far down from his career .627 (not a typo) slugging percentage there. Is it possible that his power slump in Houston was able to change the run environment that much? It seems unlikely. But something happened that year.