Moving in the Fences: A History

Colorado might be the place that most made people aware that baseball works differently in different ballparks. It was pretty hard to deny the fact that, in Colorado, hit baseballs just took off. Since people became aware of Colorado playing in a hitter-friendly stadium, many people have also become aware of San Diego and Seattle playing in pitcher-friendly stadiums. Petco Park and Safeco Field are two of baseball’s newer parks, and to date they’ve played reasonably extreme. Because of their established pitcher-friendliness, both Petco and Safeco are having their dimensions adjusted this offseason. The idea isn’t to make the ballparks hitter-friendly — it’s to make them more hitter-friendly, or basically more neutral. You bring the fences in, and it follows that offense ought to go up.

Yet it’s interesting what we can observe in recent history. I can identify four instances in which fences were moved in somewhere with the idea of helping the hitters. Between 1994-1995, the Royals made adjustments at Kauffman Stadium. Between 2002-2003, the Tigers made adjustments at Comerica Park. Between 2005-2006, the Padres made an adjustment at Petco, which obviously wasn’t enough. And, between 2011-2012, the Mets made adjustments at Citi Field. Though simple park factors are imperfect and while in certain cases we’re working with limited data, the relevant numbers are of interest. We’ll go in order.

Kauffman Stadium

This one’s tricky, because not only were the fences brought in, but they also replaced the astroturf with actual, real-live grass. These adjustments were simultaneous so one can’t be stripped entirely from the other. But anyway, the Royals figured Kauffman was too big, too pitcher-friendly. Over three years, between 1992-1994, the home-run rate at Kauffman was 70% the home-run rate in Royals games on the road. Interestingly, over the same three years, the run-scoring rate at Kauffman was 111% the run-scoring rate in Royals games on the road. Kauffman was actually already playing hitter-friendly. Over the next three years, between 1995-1997, the home-run rate at Kauffman was 95% the home-run rate in Royals games on the road. The run-scoring rate at Kauffman, however, was 99% the run-scoring rate in Royals games on the road. After the fences came in and the turf went out, Kauffman saw more homers, but fewer runs, relatively speaking.

Comerica Park

Comerica was absolutely enormous. Still is, really, but it’s less enormous than it was. A major adjustment was made to the fence in left-center field, as the Tigers worked to make the power alley more reasonable. Over three years, between 2000-2002, the home-run rate at Comerica was 68% the home-run rate in Tigers games on the road. Over the same three years, the run-scoring rate at Comerica was 93% the run-scoring rate in Tigers games on the road. Subsequently, between 2003-2005, the home-run rate at Comerica was 88% the home-run rate in Tigers games on the road. Over the same three years, the run-scoring rate at Comerica was 92% the run-scoring rate in Tigers games on the road. The homers went up, but the runs didn’t follow.

Petco Park

After two years, it felt like Petco was playing too pitcher-friendly, so the Padres made one adjustment, which clearly wasn’t good enough, since now the Padres are making more adjustments. Over two years, between 2004-2005, the home-run rate at Petco was 74% the home-run rate in Padres games on the road. Over the same two years, the run-scoring rate at Petco was 82% the run-scoring rate in Padres games on the road. After the power-alley adjustment, between 2006-2008, the home-run rate at Petco was 81% the home-run rate in Padres games on the road. Over the same three years, the run-scoring rate at Petco was 80% the run-scoring rate in Padres games on the road. Maybe you’re seeing a pattern — the homers went up, yet the runs didn’t.

Citi Field

This one’s also tricky, because the Mets made their big adjustments between 2011-2012, meaning we have but one season of post-adjustment data. But one season is better than zero seasons, and that one season can tell us something interesting. Over three years, between 2009-2011, the home-run rate at Citi was 83% the home-run rate in Mets games on the road. Over the same three years, the run-scoring rate at Citi was 91% the run-scoring rate in Mets games on the road. Then, last year, the home-run rate at Citi was 110% the home-run rate in Mets games on the road. Meanwhile, the run-scoring rate at Citi was 87% the run-scoring rate in Mets games on the road. Once again, homers up, runs not up, based at least on one season.

All of these park adjustments, of course, were different, and they’ve only been grouped together because they involved bringing the fences in. From the four examples, we see four cases in which the home-run rate improved, and four cases in which the run-scoring rate didn’t improve. In fact, in all four cases, the run-scoring rate got lower, relatively speaking, although in Citi’s case we have one season of data and in Kauffman’s case we have the simultaneous removal of astroturf. We don’t have strong conclusions; what we have is interesting evidence.

Evidence that bringing in the fences might have both intuitive and counter-intuitive effects. Park effects are complicated, meaning park adjustments are complicated. It’s easy to understand how nearer fences can mean more home runs — fly balls have to travel less distance. But that can also have other effects, like cutting down on doubles and triples, and there isn’t a perfect correlation between homer rate and run-scoring rate. If you have a pitcher-friendly ballpark, the answer might not be as simple as moving the fences closer to home plate. These things are tough to project.

Of course, what’s happened before after different adjustments might not mean anything for Petco or Safeco in 2013. No ballpark has done exactly what those two ballparks are doing. And the adjustments are being made in large part for psychological reasons — the Padres and Mariners are tired of bumming hitters out — so run-scoring might not be the key. Even if the run-scoring rates don’t change, it could be a psychological success if the home-run rates improve, because hitters want to be rewarded with dingers for their long fly balls. A place where it’s hard to hit homers feels different from a place where it’s average to hit homers, but still hard to score runs. There’s a lot going on here.

Here’s one thing we can say: going forward, it’s probably going to be easier to homer in San Diego and Seattle. Here’s one thing we can’t say: going forward, it’s probably going to be easier to score in San Diego and Seattle. That might well end up being true, but it would be wise to wait for statistical evidence. The historical record is a curious one.